diff --git a/nbgrader/docs/source/contributor_guide/metadata.rst b/nbgrader/docs/source/contributor_guide/metadata.rst
index d74f054d..4ede34a1 100644
--- a/nbgrader/docs/source/contributor_guide/metadata.rst
+++ b/nbgrader/docs/source/contributor_guide/metadata.rst
@@ -73,7 +73,8 @@ The metadata may contain the following keys:
     Added by the "Create Assignment" extension.
 
     This is the number of points that a cell is worth. It should only be
-    set if ``grade`` is also set to true.
+    set if ``grade`` is also set to true. The number of points must be greater
+    than or equal to zero.
 
 .. data:: checksum
 
diff --git a/nbgrader/nbextensions/create_assignment/main.js b/nbgrader/nbextensions/create_assignment/main.js
index 696908a4..ff4f8b3d 100644
--- a/nbgrader/nbextensions/create_assignment/main.js
+++ b/nbgrader/nbextensions/create_assignment/main.js
@@ -224,7 +224,9 @@ define([
         if (cell.metadata.nbgrader === undefined) {
             cell.metadata.nbgrader = {};
         }
-        cell.metadata.nbgrader.points = to_float(val);
+        var points = to_float(val);
+        if (points < 0) points = 0;
+        cell.metadata.nbgrader.points = points;
     };
 
     var get_grade_id = function (cell) {
diff --git a/nbgrader/nbgraderformat/v1.py b/nbgrader/nbgraderformat/v1.py
index 85afab34..5358d8d6 100644
--- a/nbgrader/nbgraderformat/v1.py
+++ b/nbgrader/nbgraderformat/v1.py
@@ -32,7 +32,11 @@ class ValidatorV1(BaseValidator):
             if meta['points'] == '':
                 meta['points'] = 0.0
             else:
-                meta['points'] = float(meta['points'])
+                points = float(meta['points'])
+                if points < 0:
+                    meta['points'] = 0.0
+                else:
+                    meta['points'] = float(meta['points'])
         else:
             meta['points'] = 0.0
 

UI allows negative points 
The UI should probably only allow points within [0-\infty] for graded cells. It currently allows negative points.

![image](https://user-images.githubusercontent.com/393899/28242040-fcc939a6-6966-11e7-9b85-9d672051646a.png)

diff --git a/nbgrader/tests/nbextensions/test_create_assignment.py b/nbgrader/tests/nbextensions/test_create_assignment.py
index da9bbc34..e972b4da 100644
--- a/nbgrader/tests/nbextensions/test_create_assignment.py
+++ b/nbgrader/tests/nbextensions/test_create_assignment.py
@@ -571,3 +571,24 @@ def test_cell_ids(browser, port):
     _save(browser)
     _wait_for_modal(browser)
     _dismiss_modal(browser)
+
+
+@pytest.mark.nbextensions
+def test_negative_points(browser, port):
+    _load_notebook(browser, port)
+    _activate_toolbar(browser)
+
+    # make sure the total points is zero
+    assert _get_total_points(browser) == 0
+
+    # make it autograder tests and set the points to two
+    _select_tests(browser)
+    _set_points(browser, points=2)
+    _set_id(browser)
+    assert _get_total_points(browser) == 2
+    assert 2 == _get_metadata(browser)['points']
+
+    # set the points to negative one
+    _set_points(browser, points=-1)
+    assert _get_total_points(browser) == 0
+    assert 0 == _get_metadata(browser)['points']
diff --git a/nbgrader/tests/nbgraderformat/test_v1.py b/nbgrader/tests/nbgraderformat/test_v1.py
index 1245aa5e..b85e4963 100644
--- a/nbgrader/tests/nbgraderformat/test_v1.py
+++ b/nbgrader/tests/nbgraderformat/test_v1.py
@@ -52,6 +52,10 @@ def test_set_points():
     ValidatorV1().upgrade_cell_metadata(cell)
     assert cell.metadata.nbgrader["points"] == 0.0
 
+    cell = create_grade_cell("", "code", "foo", -1, 0)
+    ValidatorV1().upgrade_cell_metadata(cell)
+    assert cell.metadata.nbgrader["points"] == 0.0
+
 
 def test_extra_keys():
     cell = create_grade_cell("", "code", "foo", "", 0)
@@ -65,4 +69,3 @@ def test_schema_version():
     del cell.metadata.nbgrader["schema_version"]
     ValidatorV1().upgrade_cell_metadata(cell)
     assert cell.metadata.nbgrader["schema_version"] == 1
-

pip install -r dev-requirements.txt -e .
parse_log_pytest
requirements.txt
pytest pytest-cov pytest-rerunfailures coverage selenium invoke sphinx codecov cov-core nbval
pip install -U pip wheel setuptools
3.5
dev-requirements.txt dev-requirements-windows.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
alabaster==0.7.13
alembic==1.7.7
anyio==3.6.2
argon2-cffi==21.3.0
argon2-cffi-bindings==21.2.0
async-generator==1.10
attrs==22.2.0
Babel==2.11.0
backcall==0.2.0
bleach==4.1.0
certifi==2021.5.30
cffi==1.15.1
charset-normalizer==2.0.12
codecov==2.1.13
comm==0.1.4
contextvars==2.4
cov-core==1.15.0
coverage==6.2
dataclasses==0.8
decorator==5.1.1
defusedxml==0.7.1
docutils==0.18.1
entrypoints==0.4
greenlet==2.0.2
idna==3.10
imagesize==1.4.1
immutables==0.19
importlib-metadata==4.8.3
importlib-resources==5.4.0
iniconfig==1.1.1
invoke==2.2.0
ipykernel==5.5.6
ipython==7.16.3
ipython-genutils==0.2.0
ipywidgets==7.8.5
jedi==0.17.2
Jinja2==3.0.3
json5==0.9.16
jsonschema==3.2.0
jupyter==1.1.1
jupyter-client==7.1.2
jupyter-console==6.4.3
jupyter-core==4.9.2
jupyter-server==1.13.1
jupyterlab==3.2.9
jupyterlab-pygments==0.1.2
jupyterlab-server==2.10.3
jupyterlab_widgets==1.1.11
Mako==1.1.6
MarkupSafe==2.0.1
mistune==0.8.4
nbclassic==0.3.5
nbclient==0.5.9
nbconvert==6.0.7
nbformat==5.1.3
-e git+https://github.com/jupyter/nbgrader.git@e2f288ce4a11d08db211e67b7c0d2f9ff0c5656a#egg=nbgrader
nbval==0.10.0
nest-asyncio==1.6.0
notebook==6.4.10
packaging==21.3
pandocfilters==1.5.1
parso==0.7.1
pexpect==4.9.0
pickleshare==0.7.5
pluggy==1.0.0
prometheus-client==0.17.1
prompt-toolkit==3.0.36
ptyprocess==0.7.0
py==1.11.0
pycparser==2.21
pyenchant==3.2.2
Pygments==2.14.0
pyparsing==3.1.4
pyrsistent==0.18.0
pytest==7.0.1
pytest-cov==4.0.0
pytest-rerunfailures==10.3
python-dateutil==2.9.0.post0
pytz==2025.2
pyzmq==25.1.2
requests==2.27.1
selenium==3.141.0
Send2Trash==1.8.3
six==1.17.0
sniffio==1.2.0
snowballstemmer==2.2.0
Sphinx==5.3.0
sphinx-rtd-theme==2.0.0
sphinxcontrib-applehelp==1.0.2
sphinxcontrib-devhelp==1.0.2
sphinxcontrib-htmlhelp==2.0.0
sphinxcontrib-jquery==4.1
sphinxcontrib-jsmath==1.0.1
sphinxcontrib-qthelp==1.0.3
sphinxcontrib-serializinghtml==1.1.5
sphinxcontrib-spelling==7.7.0
SQLAlchemy==1.4.54
terminado==0.12.1
testpath==0.6.0
tomli==1.2.3
tornado==6.1
traitlets==4.3.3
typing_extensions==4.1.1
urllib3==1.26.20
wcwidth==0.2.13
webencodings==0.5.1
websocket-client==1.3.1
widgetsnbextension==3.6.10
zipp==3.6.0

name: nbgrader
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2021.5.30=py36h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.3=he6710b0_2
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - python=3.6.13=h12debd9_1
  - readline=8.2=h5eee18b_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.37.1=pyhd3eb1b0_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - alabaster==0.7.13
      - alembic==1.7.7
      - anyio==3.6.2
      - argon2-cffi==21.3.0
      - argon2-cffi-bindings==21.2.0
      - async-generator==1.10
      - attrs==22.2.0
      - babel==2.11.0
      - backcall==0.2.0
      - bleach==4.1.0
      - cffi==1.15.1
      - charset-normalizer==2.0.12
      - codecov==2.1.13
      - comm==0.1.4
      - contextvars==2.4
      - cov-core==1.15.0
      - coverage==6.2
      - dataclasses==0.8
      - decorator==5.1.1
      - defusedxml==0.7.1
      - docutils==0.18.1
      - entrypoints==0.4
      - greenlet==2.0.2
      - idna==3.10
      - imagesize==1.4.1
      - immutables==0.19
      - importlib-metadata==4.8.3
      - importlib-resources==5.4.0
      - iniconfig==1.1.1
      - invoke==2.2.0
      - ipykernel==5.5.6
      - ipython==7.16.3
      - ipython-genutils==0.2.0
      - ipywidgets==7.8.5
      - jedi==0.17.2
      - jinja2==3.0.3
      - json5==0.9.16
      - jsonschema==3.2.0
      - jupyter==1.1.1
      - jupyter-client==7.1.2
      - jupyter-console==6.4.3
      - jupyter-core==4.9.2
      - jupyter-server==1.13.1
      - jupyterlab==3.2.9
      - jupyterlab-pygments==0.1.2
      - jupyterlab-server==2.10.3
      - jupyterlab-widgets==1.1.11
      - mako==1.1.6
      - markupsafe==2.0.1
      - mistune==0.8.4
      - nbclassic==0.3.5
      - nbclient==0.5.9
      - nbconvert==6.0.7
      - nbformat==5.1.3
      - nbval==0.10.0
      - nest-asyncio==1.6.0
      - notebook==6.4.10
      - packaging==21.3
      - pandocfilters==1.5.1
      - parso==0.7.1
      - pexpect==4.9.0
      - pickleshare==0.7.5
      - pip==21.3.1
      - pluggy==1.0.0
      - prometheus-client==0.17.1
      - prompt-toolkit==3.0.36
      - ptyprocess==0.7.0
      - py==1.11.0
      - pycparser==2.21
      - pyenchant==3.2.2
      - pygments==2.14.0
      - pyparsing==3.1.4
      - pyrsistent==0.18.0
      - pytest==7.0.1
      - pytest-cov==4.0.0
      - pytest-rerunfailures==10.3
      - python-dateutil==2.9.0.post0
      - pytz==2025.2
      - pyzmq==25.1.2
      - requests==2.27.1
      - selenium==3.141.0
      - send2trash==1.8.3
      - setuptools==59.6.0
      - six==1.17.0
      - sniffio==1.2.0
      - snowballstemmer==2.2.0
      - sphinx==5.3.0
      - sphinx-rtd-theme==2.0.0
      - sphinxcontrib-applehelp==1.0.2
      - sphinxcontrib-devhelp==1.0.2
      - sphinxcontrib-htmlhelp==2.0.0
      - sphinxcontrib-jquery==4.1
      - sphinxcontrib-jsmath==1.0.1
      - sphinxcontrib-qthelp==1.0.3
      - sphinxcontrib-serializinghtml==1.1.5
      - sphinxcontrib-spelling==7.7.0
      - sqlalchemy==1.4.54
      - terminado==0.12.1
      - testpath==0.6.0
      - tomli==1.2.3
      - tornado==6.1
      - traitlets==4.3.3
      - typing-extensions==4.1.1
      - urllib3==1.26.20
      - wcwidth==0.2.13
      - webencodings==0.5.1
      - websocket-client==1.3.1
      - widgetsnbextension==3.6.10
      - zipp==3.6.0
prefix: /opt/conda/envs/nbgrader

nbgrader/tests/nbgraderformat/test_v1.py::test_set_points
nbgrader/tests/nbgraderformat/test_v1.py::test_set_false nbgrader/tests/nbgraderformat/test_v1.py::test_remove_metadata nbgrader/tests/nbgraderformat/test_v1.py::test_remove_points nbgrader/tests/nbgraderformat/test_v1.py::test_extra_keys nbgrader/tests/nbgraderformat/test_v1.py::test_schema_version
nbgrader/docs/source/contributor_guide/metadata.rst nbgrader/nbextensions/create_assignment/main.js nbgrader/nbgraderformat/v1.py
nbgrader/docs/source/contributor_guide/metadata.rst nbgrader/nbextensions/create_assignment/main.js nbgrader/nbgraderformat/v1.py