diff --git a/nbgrader/apps/api.py b/nbgrader/apps/api.py
index 37dbc379b..0480647c6 100644
--- a/nbgrader/apps/api.py
+++ b/nbgrader/apps/api.py
@@ -1066,9 +1066,10 @@ def generate_feedback(self, assignment_id, student_id=None, force=True):
         """
         # Because we may be using HTMLExporter.template_file in other
         # parts of the the UI, we need to make sure that the template
-        # is explicitply 'feedback.tpl` here:
+        # is explicitly 'feedback.html.j2` here:
         c = Config()
-        c.HTMLExporter.template_file = 'feedback.tpl'
+        c.HTMLExporter.template_name = 'feedback'
+        c.HTMLExporter.template_file = 'feedback.html.j2'
         if student_id is not None:
             with temp_attrs(self.coursedir,
                             assignment_id=assignment_id,
diff --git a/nbgrader/apps/nbgraderapp.py b/nbgrader/apps/nbgraderapp.py
index ba648fd7b..fb9c5b5c2 100755
--- a/nbgrader/apps/nbgraderapp.py
+++ b/nbgrader/apps/nbgraderapp.py
@@ -4,6 +4,7 @@
 import sys
 import os
 
+import asyncio
 from textwrap import dedent
 
 from traitlets import default
@@ -53,6 +54,12 @@
 })
 
 
+# See https://bugs.python.org/issue37373 :(
+# Workaround from https://github.com/jupyter/nbconvert/issues/1372
+if sys.version_info[0] == 3 and sys.version_info[1] >= 8 and sys.platform.startswith('win'):
+    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
+
+
 class NbGraderApp(NbGrader):
 
     name = u'nbgrader'
diff --git a/nbgrader/converters/autograde.py b/nbgrader/converters/autograde.py
index ec002b2ef..7f0ced0da 100644
--- a/nbgrader/converters/autograde.py
+++ b/nbgrader/converters/autograde.py
@@ -7,7 +7,7 @@
 from .base import BaseConverter, NbGraderException
 from ..preprocessors import (
     AssignLatePenalties, ClearOutput, DeduplicateIds, OverwriteCells, SaveAutoGrades,
-    Execute, LimitOutput, OverwriteKernelspec, CheckCellMetadata)
+    Execute, LimitOutput, OverwriteKernelspec, CheckCellMetadata, RemoveExecutionInfo)
 from ..api import Gradebook, MissingEntry
 from .. import utils
 
@@ -59,6 +59,7 @@ def _output_directory(self) -> str:
     ]).tag(config=True)
     autograde_preprocessors = List([
         Execute,
+        RemoveExecutionInfo,
         LimitOutput,
         SaveAutoGrades,
         AssignLatePenalties,
diff --git a/nbgrader/converters/generate_feedback.py b/nbgrader/converters/generate_feedback.py
index 7bb1459da..75d88cd02 100644
--- a/nbgrader/converters/generate_feedback.py
+++ b/nbgrader/converters/generate_feedback.py
@@ -55,9 +55,8 @@ def _load_config(self, cfg, **kwargs):
     def __init__(self, coursedir=None, **kwargs):
         super(GenerateFeedback, self).__init__(coursedir=coursedir, **kwargs)
         c = Config()
-        if 'template_file' not in self.config.HTMLExporter:
-            c.HTMLExporter.template_file = 'feedback.tpl'
-        if 'template_path' not in self.config.HTMLExporter:
-            template_path = os.path.abspath(os.path.join(os.path.dirname(__file__), '..', 'server_extensions', 'formgrader', 'templates'))
-            c.HTMLExporter.template_path = ['.', template_path]
+        c.HTMLExporter.template_name = 'feedback'
+        c.HTMLExporter.template_file = 'feedback.html.j2'
+        template_path = os.path.abspath(os.path.join(os.path.dirname(__file__), '..', 'server_extensions', 'formgrader', 'templates'))
+        c.HTMLExporter.extra_template_basedirs.append(template_path)
         self.update_config(c)
diff --git a/nbgrader/preprocessors/__init__.py b/nbgrader/preprocessors/__init__.py
index 1507ee0aa..f58381d47 100644
--- a/nbgrader/preprocessors/__init__.py
+++ b/nbgrader/preprocessors/__init__.py
@@ -16,6 +16,7 @@
 from .clearhiddentests import ClearHiddenTests
 from .clearmarkingscheme import ClearMarkScheme
 from .overwritekernelspec import OverwriteKernelspec
+from .removeexecutioninfo import RemoveExecutionInfo
 
 __all__ = [
     "AssignLatePenalties",
@@ -35,4 +36,5 @@
     "ClearHiddenTests",
     "ClearMarkScheme",
     "OverwriteKernelspec",
+    "RemoveExecutionInfo"
 ]
diff --git a/nbgrader/preprocessors/execute.py b/nbgrader/preprocessors/execute.py
index 29b09ea0f..3048b6517 100644
--- a/nbgrader/preprocessors/execute.py
+++ b/nbgrader/preprocessors/execute.py
@@ -5,7 +5,7 @@
 from . import NbGraderPreprocessor
 from nbconvert.exporters.exporter import ResourcesDict
 from nbformat.notebooknode import NotebookNode
-from typing import Any, Optional, Tuple
+from typing import Any, Optional, Tuple, Dict
 
 
 class UnresponsiveKernelError(Exception):
@@ -56,50 +56,48 @@ def preprocess(self,
 
         return output
 
-    def preprocess_cell(self, cell, resources, cell_index, store_history=True):
-            """
-            Need to override preprocess_cell to check reply for errors
-            """
-            # Copied from nbconvert ExecutePreprocessor
-            if cell.cell_type != 'code' or not cell.source.strip():
-                return cell, resources
-
-            reply, outputs = self.run_cell(cell, cell_index, store_history)
-            # Backwards compatibility for processes that wrap run_cell
-            cell.outputs = outputs
-
-            cell_allows_errors = (self.allow_errors or "raises-exception"
-                                in cell.metadata.get("tags", []))
-
-            if self.force_raise_errors or not cell_allows_errors:
-                if (reply is not None) and reply['content']['status'] == 'error':
-                    raise CellExecutionError.from_cell_and_msg(cell, reply['content'])
-
-            # Ensure errors are recorded to prevent false positives when autograding
-            if (reply is None) or reply['content']['status'] == 'error':
-                error_recorded = False
-                for output in cell.outputs:
-                    if output.output_type == 'error':
-                        error_recorded = True
-                if not error_recorded:
-                    error_output = NotebookNode(output_type='error')
-                    if reply is None:
-                        # Occurs when
-                        # IPython.core.interactiveshell.InteractiveShell.showtraceback
-                        # = None
-                        error_output.ename = "CellTimeoutError"
-                        error_output.evalue = ""
-                        error_output.traceback = ["ERROR: No reply from kernel"]
-                    else:
-                        # Occurs when
-                        # IPython.core.interactiveshell.InteractiveShell.showtraceback
-                        # = lambda *args, **kwargs : None
-                        error_output.ename = reply['content']['ename']
-                        error_output.evalue = reply['content']['evalue']
-                        error_output.traceback = reply['content']['traceback']
-                        if error_output.traceback == []:
-                            error_output.traceback = ["ERROR: An error occurred while"
-                                                      " showtraceback was disabled"]
-                    cell.outputs.append(error_output)
-
-            return cell, resources
+    def _check_raise_for_error(
+            self,
+            cell: NotebookNode,
+            exec_reply: Optional[Dict]) -> None:
+
+        exec_reply_content = None
+        if exec_reply is not None:
+            exec_reply_content = exec_reply['content']
+            if exec_reply_content['status'] != 'error':
+                return None
+
+            cell_allows_errors = (not self.force_raise_errors) and (
+                self.allow_errors
+                or exec_reply_content.get('ename') in self.allow_error_names
+                or "raises-exception" in cell.metadata.get("tags", []))
+
+            if not cell_allows_errors:
+                raise CellExecutionError.from_cell_and_msg(cell, exec_reply_content)
+
+        # Ensure errors are recorded to prevent false positives when autograding
+        if exec_reply is None or exec_reply_content['status'] == 'error':
+            error_recorded = False
+            for output in cell.outputs:
+                if output.output_type == 'error':
+                    error_recorded = True
+                    break
+
+            if not error_recorded:
+                error_output = NotebookNode(output_type='error')
+                if exec_reply is None:
+                    # Occurs when
+                    # IPython.core.interactiveshell.InteractiveShell.showtraceback = None
+                    error_output.ename = "CellTimeoutError"
+                    error_output.evalue = ""
+                    error_output.traceback = ["ERROR: No reply from kernel"]
+                else:
+                    # Occurs when
+                    # IPython.core.interactiveshell.InteractiveShell.showtraceback = lambda *args, **kwargs: None
+                    error_output.ename = exec_reply_content['ename']
+                    error_output.evalue = exec_reply_content['evalue']
+                    error_output.traceback = exec_reply_content['traceback']
+                    if error_output.traceback == []:
+                        error_output.traceback = ["ERROR: An error occurred while"
+                                                  " showtraceback was disabled"]
+                cell.outputs.append(error_output)
diff --git a/nbgrader/preprocessors/getgrades.py b/nbgrader/preprocessors/getgrades.py
index 6dfbbbe5b..2f28bfefb 100644
--- a/nbgrader/preprocessors/getgrades.py
+++ b/nbgrader/preprocessors/getgrades.py
@@ -42,6 +42,9 @@ def preprocess(self,
             resources['nbgrader']['max_score'] = notebook.max_score
             resources['nbgrader']['late_penalty'] = late_penalty
 
+        # Set title
+        nb['metadata']['title'] = resources['nbgrader']['notebook']
+
         return nb, resources
 
     def _get_comment(self, cell: NotebookNode, resources: ResourcesDict) -> None:
diff --git a/nbgrader/preprocessors/removeexecutioninfo.py b/nbgrader/preprocessors/removeexecutioninfo.py
new file mode 100644
index 000000000..b07ee3a7c
--- /dev/null
+++ b/nbgrader/preprocessors/removeexecutioninfo.py
@@ -0,0 +1,19 @@
+from . import NbGraderPreprocessor
+
+from traitlets import Integer
+from nbformat.notebooknode import NotebookNode
+from nbconvert.exporters.exporter import ResourcesDict
+from typing import Tuple
+
+
+class RemoveExecutionInfo(NbGraderPreprocessor):
+    """Preprocessor for removing execution info."""
+
+    def preprocess_cell(self,
+                        cell: NotebookNode,
+                        resources: ResourcesDict,
+                        cell_index: int
+                        ) -> Tuple[NotebookNode, ResourcesDict]:
+        if 'execution' in cell['metadata']:
+            del cell['metadata']['execution']
+        return cell, resources
diff --git a/nbgrader/server_extensions/formgrader/base.py b/nbgrader/server_extensions/formgrader/base.py
index 795add503..5526f15ab 100644
--- a/nbgrader/server_extensions/formgrader/base.py
+++ b/nbgrader/server_extensions/formgrader/base.py
@@ -62,19 +62,19 @@ def render(self, name, **ns):
     def write_error(self, status_code, **kwargs):
         if status_code == 500:
             html = self.render(
-                'base_500.tpl',
+                'pages/base_500.html.j2',
                 base_url=self.base_url,
                 error_code=500)
 
         elif status_code == 502:
             html = self.render(
-                'base_500.tpl',
+                'pages/base_500.html.j2',
                 base_url=self.base_url,
                 error_code=502)
 
         elif status_code == 403:
             html = self.render(
-                'base_403.tpl',
+                'pages/base_403.html.j2',
                 base_url=self.base_url,
                 error_code=403)
 
diff --git a/nbgrader/server_extensions/formgrader/formgrader.py b/nbgrader/server_extensions/formgrader/formgrader.py
index 7ba769aef..dc0254f3c 100644
--- a/nbgrader/server_extensions/formgrader/formgrader.py
+++ b/nbgrader/server_extensions/formgrader/formgrader.py
@@ -25,13 +25,17 @@ def _classes_default(self):
 
     def build_extra_config(self):
         extra_config = super(FormgradeExtension, self).build_extra_config()
-        extra_config.HTMLExporter.template_file = 'formgrade'
-        extra_config.HTMLExporter.template_path = [handlers.template_path]
+        extra_config.HTMLExporter.template_name = 'formgrade'
+        extra_config.HTMLExporter.template_file = 'formgrade.html.j2'
+        extra_config.HTMLExporter.extra_template_basedirs.append(handlers.template_path)
         return extra_config
 
     def init_tornado_settings(self, webapp):
         # Init jinja environment
-        jinja_env = Environment(loader=FileSystemLoader([handlers.template_path]))
+        jinja_env = Environment(loader=FileSystemLoader([
+            os.path.join(handlers.template_path, 'formgrade'),
+            os.path.join(handlers.template_path, 'pages')
+        ]))
 
         course_dir = self.coursedir.root
         notebook_dir = self.parent.notebook_dir
diff --git a/nbgrader/server_extensions/formgrader/handlers.py b/nbgrader/server_extensions/formgrader/handlers.py
index 2143eca17..025ec0ecb 100644
--- a/nbgrader/server_extensions/formgrader/handlers.py
+++ b/nbgrader/server_extensions/formgrader/handlers.py
@@ -14,7 +14,7 @@ class ManageAssignmentsHandler(BaseHandler):
     @check_notebook_dir
     def get(self):
         html = self.render(
-            "manage_assignments.tpl",
+            "manage_assignments.html.j2",
             url_prefix=self.url_prefix,
             base_url=self.base_url,
             windows=(sys.prefix == 'win32'),
@@ -30,7 +30,7 @@ class ManageSubmissionsHandler(BaseHandler):
     @check_notebook_dir
     def get(self, assignment_id):
         html = self.render(
-            "manage_submissions.tpl",
+            "manage_submissions.html.j2",
             course_dir=self.coursedir.root,
             assignment_id=assignment_id,
             base_url=self.base_url)
@@ -43,7 +43,7 @@ class GradebookAssignmentsHandler(BaseHandler):
     @check_notebook_dir
     def get(self):
         html = self.render(
-            "gradebook_assignments.tpl",
+            "gradebook_assignments.html.j2",
             base_url=self.base_url)
         self.write(html)
 
@@ -54,7 +54,7 @@ class GradebookNotebooksHandler(BaseHandler):
     @check_notebook_dir
     def get(self, assignment_id):
         html = self.render(
-            "gradebook_notebooks.tpl",
+            "gradebook_notebooks.html.j2",
             assignment_id=assignment_id,
             base_url=self.base_url)
         self.write(html)
@@ -66,7 +66,7 @@ class GradebookNotebookSubmissionsHandler(BaseHandler):
     @check_notebook_dir
     def get(self, assignment_id, notebook_id):
         html = self.render(
-            "gradebook_notebook_submissions.tpl",
+            "gradebook_notebook_submissions.html.j2",
             assignment_id=assignment_id,
             notebook_id=notebook_id,
             base_url=self.base_url
@@ -116,7 +116,7 @@ def get(self, submission_id):
 
         if not os.path.exists(filename):
             resources['filename'] = filename
-            html = self.render('formgrade_404.tpl', resources=resources)
+            html = self.render('formgrade_404.html.j2', resources=resources)
             self.clear()
             self.set_status(404)
             self.write(html)
@@ -235,7 +235,7 @@ class ManageStudentsHandler(BaseHandler):
     @check_notebook_dir
     def get(self):
         html = self.render(
-            "manage_students.tpl",
+            "manage_students.html.j2",
             base_url=self.base_url)
         self.write(html)
 
@@ -246,7 +246,7 @@ class ManageStudentsAssignmentsHandler(BaseHandler):
     @check_notebook_dir
     def get(self, student_id):
         html = self.render(
-            "manage_students_assignments.tpl",
+            "manage_students_assignments.html.j2",
             student_id=student_id,
             base_url=self.base_url)
 
@@ -259,7 +259,7 @@ class ManageStudentNotebookSubmissionsHandler(BaseHandler):
     @check_notebook_dir
     def get(self, student_id, assignment_id):
         html = self.render(
-            "manage_students_notebook_submissions.tpl",
+            "manage_students_notebook_submissions.html.j2",
             assignment_id=assignment_id,
             student_id=student_id,
             base_url=self.base_url
diff --git a/nbgrader/server_extensions/formgrader/templates/feedback/conf.json b/nbgrader/server_extensions/formgrader/templates/feedback/conf.json
new file mode 100644
index 000000000..aa66ccd95
--- /dev/null
+++ b/nbgrader/server_extensions/formgrader/templates/feedback/conf.json
@@ -0,0 +1,7 @@
+{
+    "base_template": "classic",
+    "mimetypes": {
+        "text/html": true
+    },
+    "preprocessors": {}
+}
\ No newline at end of file
diff --git a/nbgrader/server_extensions/formgrader/templates/feedback.tpl b/nbgrader/server_extensions/formgrader/templates/feedback/feedback.html.j2
similarity index 85%
rename from nbgrader/server_extensions/formgrader/templates/feedback.tpl
rename to nbgrader/server_extensions/formgrader/templates/feedback/feedback.html.j2
index f28c54e5e..dd424cdc6 100644
--- a/nbgrader/server_extensions/formgrader/templates/feedback.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/feedback/feedback.html.j2
@@ -1,60 +1,12 @@
-{%- extends 'basic.tpl' -%}
-{% from 'mathjax.tpl' import mathjax %}
-
-{%- block header -%}
-<!DOCTYPE html>
-<html>
-<head>
-
-<meta charset="utf-8" />
-<title>{{ resources.nbgrader.notebook }}</title>
-
-{% for css in resources.inlining.css -%}
-    <style type="text/css">
-    {{ css }}
-    </style>
-{% endfor %}
-
-<!-- Loading mathjax macro -->
-{{ mathjax() }}
-
-<style>
-td.center, th.center {
-    text-align: center;
-}
-
-body {
-  overflow: visible;
-  font-size: 14px;
-  padding-top: 1em;
-}
-
-div#notebook {
-  overflow: visible;
-  border-top: none;
-}
+{%- extends 'index.html.j2' -%}
+{% from 'mathjax.html.j2' import mathjax %}
 
+{%- block html_head_css -%}
+<style type="text/css">
 div#notebook-container {
   width: 100%;
-}
-
-@media print {
-  div.cell {
-    display: block;
-    page-break-inside: avoid;
-  }
-  div.output_wrapper {
-    display: block;
-    page-break-inside: avoid;
-  }
-  div.output {
-    display: block;
-    page-break-inside: avoid;
-  }
-}
-
-div.prompt {
-  min-width: 21ex;
+  -webkit-box-shadow: none;
+  box-shadow: none;
 }
 
 div.nbgrader_cell {
@@ -105,9 +57,8 @@ span.nbgrader-label {
     top: 4px;
 }
 </style>
+{% endblock html_head_css %}
 
-</head>
-{%- endblock header -%}
 
 {% block body %}
 <body>
@@ -139,20 +90,13 @@ span.nbgrader-label {
         </div>
       </div>
       <div class="panel-body">
-        <div id="notebook" class="border-box-sizing">
-          <div class="container" id="notebook-container">
-            {{ super() }}
-          </div>
-        </div>
+        {{ super() }}
       </div>
     </div>
   </div>
 </body>
 {%- endblock body %}
 
-{% block footer %}
-</html>
-{% endblock footer %}
 
 {% macro score(cell) -%}
   <span class="pull-right">
diff --git a/nbgrader/server_extensions/formgrader/templates/formgrade/conf.json b/nbgrader/server_extensions/formgrader/templates/formgrade/conf.json
new file mode 100644
index 000000000..aa66ccd95
--- /dev/null
+++ b/nbgrader/server_extensions/formgrader/templates/formgrade/conf.json
@@ -0,0 +1,7 @@
+{
+    "base_template": "classic",
+    "mimetypes": {
+        "text/html": true
+    },
+    "preprocessors": {}
+}
\ No newline at end of file
diff --git a/nbgrader/server_extensions/formgrader/templates/formgrade.tpl b/nbgrader/server_extensions/formgrader/templates/formgrade/formgrade.html.j2
similarity index 97%
rename from nbgrader/server_extensions/formgrader/templates/formgrade.tpl
rename to nbgrader/server_extensions/formgrader/templates/formgrade/formgrade.html.j2
index 0822b7f72..476ff41f9 100644
--- a/nbgrader/server_extensions/formgrader/templates/formgrade.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/formgrade/formgrade.html.j2
@@ -1,6 +1,6 @@
-{%- extends 'basic.tpl' -%}
-{% from 'formgrade_macros.tpl' import nav, header %}
-{% from 'mathjax.tpl' import mathjax %}
+{%- extends 'index.html.j2' -%}
+{% from 'formgrade_macros.html.j2' import nav, header %}
+{% from 'mathjax.html.j2' import mathjax %}
 
 {%- block header -%}
 <!DOCTYPE html>
diff --git a/nbgrader/server_extensions/formgrader/templates/formgrade_404.tpl b/nbgrader/server_extensions/formgrader/templates/formgrade/formgrade_404.html.j2
similarity index 93%
rename from nbgrader/server_extensions/formgrader/templates/formgrade_404.tpl
rename to nbgrader/server_extensions/formgrader/templates/formgrade/formgrade_404.html.j2
index 0353bcefd..ed79f9a3b 100644
--- a/nbgrader/server_extensions/formgrader/templates/formgrade_404.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/formgrade/formgrade_404.html.j2
@@ -1,4 +1,4 @@
-{% from 'formgrade_macros.tpl' import nav, header %}
+{% from 'formgrade_macros.html.j2' import nav, header %}
 
 <!DOCTYPE html>
 <html>
diff --git a/nbgrader/server_extensions/formgrader/templates/formgrade_macros.tpl b/nbgrader/server_extensions/formgrader/templates/formgrade/formgrade_macros.html.j2
similarity index 100%
rename from nbgrader/server_extensions/formgrader/templates/formgrade_macros.tpl
rename to nbgrader/server_extensions/formgrader/templates/formgrade/formgrade_macros.html.j2
diff --git a/nbgrader/server_extensions/formgrader/templates/base.tpl b/nbgrader/server_extensions/formgrader/templates/pages/base.html.j2
similarity index 100%
rename from nbgrader/server_extensions/formgrader/templates/base.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/base.html.j2
diff --git a/nbgrader/server_extensions/formgrader/templates/base_403.tpl b/nbgrader/server_extensions/formgrader/templates/pages/base_403.html.j2
similarity index 87%
rename from nbgrader/server_extensions/formgrader/templates/base_403.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/base_403.html.j2
index 6b29da31b..8178827c3 100644
--- a/nbgrader/server_extensions/formgrader/templates/base_403.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/base_403.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'base.tpl' -%}
+{%- extends 'base.html.j2' -%}
 
 {%- block title -%}
 Not Authorized
diff --git a/nbgrader/server_extensions/formgrader/templates/base_500.tpl b/nbgrader/server_extensions/formgrader/templates/pages/base_500.html.j2
similarity index 89%
rename from nbgrader/server_extensions/formgrader/templates/base_500.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/base_500.html.j2
index 6dfe7789a..c4854a62d 100644
--- a/nbgrader/server_extensions/formgrader/templates/base_500.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/base_500.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'base.tpl' -%}
+{%- extends 'base.html.j2' -%}
 
 {%- block title -%}
 Error
diff --git a/nbgrader/server_extensions/formgrader/templates/gradebook_assignments.tpl b/nbgrader/server_extensions/formgrader/templates/pages/gradebook_assignments.html.j2
similarity index 92%
rename from nbgrader/server_extensions/formgrader/templates/gradebook_assignments.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/gradebook_assignments.html.j2
index 06390b490..481f4fc9c 100644
--- a/nbgrader/server_extensions/formgrader/templates/gradebook_assignments.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/gradebook_assignments.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'gradebook_base.tpl' -%}
+{%- extends 'gradebook_base.html.j2' -%}
 
 {%- block head -%}
 <script src="{{ base_url }}/formgrader/static/js/gradebook_assignments.js"></script>
diff --git a/nbgrader/server_extensions/formgrader/templates/gradebook_base.tpl b/nbgrader/server_extensions/formgrader/templates/pages/gradebook_base.html.j2
similarity index 92%
rename from nbgrader/server_extensions/formgrader/templates/gradebook_base.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/gradebook_base.html.j2
index e280d7312..4f510c9fe 100644
--- a/nbgrader/server_extensions/formgrader/templates/gradebook_base.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/gradebook_base.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'base.tpl' -%}
+{%- extends 'base.html.j2' -%}
 
 {%- block title -%}
 Manual Grading
diff --git a/nbgrader/server_extensions/formgrader/templates/gradebook_notebook_submissions.tpl b/nbgrader/server_extensions/formgrader/templates/pages/gradebook_notebook_submissions.html.j2
similarity index 96%
rename from nbgrader/server_extensions/formgrader/templates/gradebook_notebook_submissions.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/gradebook_notebook_submissions.html.j2
index caa8b640c..0bb1dce30 100644
--- a/nbgrader/server_extensions/formgrader/templates/gradebook_notebook_submissions.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/gradebook_notebook_submissions.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'gradebook_base.tpl' -%}
+{%- extends 'gradebook_base.html.j2' -%}
 
 {%- block head -%}
 <script>
diff --git a/nbgrader/server_extensions/formgrader/templates/gradebook_notebooks.tpl b/nbgrader/server_extensions/formgrader/templates/pages/gradebook_notebooks.html.j2
similarity index 95%
rename from nbgrader/server_extensions/formgrader/templates/gradebook_notebooks.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/gradebook_notebooks.html.j2
index 93220c647..2278165cb 100644
--- a/nbgrader/server_extensions/formgrader/templates/gradebook_notebooks.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/gradebook_notebooks.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'gradebook_base.tpl' -%}
+{%- extends 'gradebook_base.html.j2' -%}
 
 {%- block head -%}
 <script>
diff --git a/nbgrader/server_extensions/formgrader/templates/manage_assignments.tpl b/nbgrader/server_extensions/formgrader/templates/pages/manage_assignments.html.j2
similarity index 99%
rename from nbgrader/server_extensions/formgrader/templates/manage_assignments.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/manage_assignments.html.j2
index 51b6969f8..cf141f875 100644
--- a/nbgrader/server_extensions/formgrader/templates/manage_assignments.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/manage_assignments.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'base.tpl' -%}
+{%- extends 'base.html.j2' -%}
 
 {%- block head -%}
 <script>
diff --git a/nbgrader/server_extensions/formgrader/templates/manage_students.tpl b/nbgrader/server_extensions/formgrader/templates/pages/manage_students.html.j2
similarity index 94%
rename from nbgrader/server_extensions/formgrader/templates/manage_students.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/manage_students.html.j2
index 09de65521..7d356bb25 100644
--- a/nbgrader/server_extensions/formgrader/templates/manage_students.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/manage_students.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'manage_students_base.tpl' -%}
+{%- extends 'manage_students_base.html.j2' -%}
 
 {%- block head -%}
 <script src="{{ base_url }}/formgrader/static/js/manage_students.js"></script>
diff --git a/nbgrader/server_extensions/formgrader/templates/manage_students_assignments.tpl b/nbgrader/server_extensions/formgrader/templates/pages/manage_students_assignments.html.j2
similarity index 94%
rename from nbgrader/server_extensions/formgrader/templates/manage_students_assignments.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/manage_students_assignments.html.j2
index 90a7139a4..ff3b77a73 100644
--- a/nbgrader/server_extensions/formgrader/templates/manage_students_assignments.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/manage_students_assignments.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'manage_students_base.tpl' -%}
+{%- extends 'manage_students_base.html.j2' -%}
 
 {%- block head -%}
 <script>
diff --git a/nbgrader/server_extensions/formgrader/templates/manage_students_base.tpl b/nbgrader/server_extensions/formgrader/templates/pages/manage_students_base.html.j2
similarity index 92%
rename from nbgrader/server_extensions/formgrader/templates/manage_students_base.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/manage_students_base.html.j2
index 86ecf3399..69bcc647d 100644
--- a/nbgrader/server_extensions/formgrader/templates/manage_students_base.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/manage_students_base.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'base.tpl' -%}
+{%- extends 'base.html.j2' -%}
 
 {%- block title -%}
 Manage Students
diff --git a/nbgrader/server_extensions/formgrader/templates/manage_students_notebook_submissions.tpl b/nbgrader/server_extensions/formgrader/templates/pages/manage_students_notebook_submissions.html.j2
similarity index 95%
rename from nbgrader/server_extensions/formgrader/templates/manage_students_notebook_submissions.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/manage_students_notebook_submissions.html.j2
index 0666f4188..aa85d7d31 100644
--- a/nbgrader/server_extensions/formgrader/templates/manage_students_notebook_submissions.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/manage_students_notebook_submissions.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'manage_students_base.tpl' -%}
+{%- extends 'manage_students_base.html.j2' -%}
 
 {%- block head -%}
 <script>
diff --git a/nbgrader/server_extensions/formgrader/templates/manage_submissions.tpl b/nbgrader/server_extensions/formgrader/templates/pages/manage_submissions.html.j2
similarity index 98%
rename from nbgrader/server_extensions/formgrader/templates/manage_submissions.tpl
rename to nbgrader/server_extensions/formgrader/templates/pages/manage_submissions.html.j2
index 326223892..6c8528b08 100644
--- a/nbgrader/server_extensions/formgrader/templates/manage_submissions.tpl
+++ b/nbgrader/server_extensions/formgrader/templates/pages/manage_submissions.html.j2
@@ -1,4 +1,4 @@
-{%- extends 'base.tpl' -%}
+{%- extends 'base.html.j2' -%}
 
 {%- block head -%}
 <script>
diff --git a/nbgrader/tests/apps/files/submitted-cheat-attempt-alternative.ipynb b/nbgrader/tests/apps/files/submitted-cheat-attempt-alternative.ipynb
index 1632063c0..35b2bf840 100644
--- a/nbgrader/tests/apps/files/submitted-cheat-attempt-alternative.ipynb
+++ b/nbgrader/tests/apps/files/submitted-cheat-attempt-alternative.ipynb
@@ -4,7 +4,6 @@
    "cell_type": "code",
    "execution_count": null,
    "metadata": {
-    "collapsed": true,
     "deletable": false,
     "nbgrader": {
      "cell_type": "code",
@@ -20,14 +19,13 @@
    "source": [
     "# YOUR CODE HERE\n",
     "import IPython.core.interactiveshell\n",
-    "IPython.core.interactiveshell.InteractiveShell.showtraceback = None"
+    "IPython.core.interactiveshell.InteractiveShell.showtraceback = lambda *args, **kwargs: None"
    ]
   },
   {
    "cell_type": "code",
    "execution_count": null,
    "metadata": {
-    "collapsed": true,
     "deletable": false,
     "nbgrader": {
      "cell_type": "code",
@@ -35,7 +33,7 @@
      "grade": true,
      "grade_id": "foo",
      "locked": false,
-     "points": 1.0,
+     "points": 1,
      "schema_version": 3,
      "solution": false
     }
@@ -49,7 +47,6 @@
    "cell_type": "code",
    "execution_count": null,
    "metadata": {
-    "collapsed": true,
     "deletable": false,
     "nbgrader": {
      "cell_type": "code",
@@ -57,7 +54,7 @@
      "grade": true,
      "grade_id": "bar",
      "locked": false,
-     "points": 1.0,
+     "points": 1,
      "schema_version": 3,
      "solution": false
     }
@@ -77,7 +74,7 @@
      "grade": true,
      "grade_id": "baz",
      "locked": false,
-     "points": 2.0,
+     "points": 2,
      "schema_version": 3,
      "solution": true
     }
@@ -90,14 +87,13 @@
    "cell_type": "code",
    "execution_count": null,
    "metadata": {
-    "collapsed": true,
     "nbgrader": {
      "cell_type": "code",
      "checksum": "5a193c164d7b444efe9a3612bee09f4c",
      "grade": true,
      "grade_id": "quux",
      "locked": false,
-     "points": 3.0,
+     "points": 3,
      "schema_version": 3,
      "solution": true
     }
@@ -112,7 +108,6 @@
    "cell_type": "code",
    "execution_count": null,
    "metadata": {
-    "collapsed": true,
     "nbgrader": {
      "cell_type": "code",
      "checksum": "86f5f877fe95faac003fcd4b8d43d093",
@@ -148,11 +143,23 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python",
+   "display_name": "Python 3",
    "language": "python",
-   "name": "python"
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.9.2"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 0
+ "nbformat_minor": 1
 }
diff --git a/setup.py b/setup.py
index 6d81376c9..437205fa4 100644
--- a/setup.py
+++ b/setup.py
@@ -91,7 +91,7 @@
         "python-dateutil",
         "jupyter",
         "notebook>=4.2",
-        "nbconvert==5.6.1",
+        "nbconvert>=6.0.7",
         "nbformat",
         "traitlets==4.3.3",
         "jupyter_core",