diff --git a/lms/djangoapps/grades/api/v1/tests/test_views.py b/lms/djangoapps/grades/api/v1/tests/test_views.py
index 1f26c20643..38063958fc 100644
--- a/lms/djangoapps/grades/api/v1/tests/test_views.py
+++ b/lms/djangoapps/grades/api/v1/tests/test_views.py
@@ -889,6 +889,28 @@ class GradebookBulkUpdateViewTest(GradebookViewTestBase):
             )
             self.assertEqual(status.HTTP_404_NOT_FOUND, resp.status_code)
 
+    def test_grades_frozen(self):
+        """
+        Should receive a 403 when grades have been frozen for a course.
+        """
+        with patch('lms.djangoapps.grades.api.v1.views.are_grades_frozen', return_value=True):
+            with override_waffle_flag(self.waffle_flag, active=True):
+                self.login_staff()
+                post_data = [
+                    {
+                        'user_id': self.student.id,
+                        'usage_id': text_type(self.subsections[self.chapter_1.location][0].location),
+                        'grade': {},  # doesn't matter what we put here.
+                    }
+                ]
+
+                resp = self.client.post(
+                    self.get_url(),
+                    data=json.dumps(post_data),
+                    content_type='application/json',
+                )
+                self.assertEqual(status.HTTP_403_FORBIDDEN, resp.status_code)
+
     def test_user_not_enrolled(self):
         with override_waffle_flag(self.waffle_flag, active=True):
             self.login_staff()
diff --git a/lms/djangoapps/grades/api/v1/views.py b/lms/djangoapps/grades/api/v1/views.py
index cc505d7778..a3a7747779 100644
--- a/lms/djangoapps/grades/api/v1/views.py
+++ b/lms/djangoapps/grades/api/v1/views.py
@@ -25,9 +25,8 @@ from lms.djangoapps.grades.course_data import CourseData
 from lms.djangoapps.grades.course_grade_factory import CourseGradeFactory
 from lms.djangoapps.grades.events import SUBSECTION_GRADE_CALCULATED, subsection_grade_calculated
 from lms.djangoapps.grades.models import PersistentSubsectionGrade, PersistentSubsectionGradeOverride
-from lms.djangoapps.grades.signals import signals
 from lms.djangoapps.grades.subsection_grade import CreateSubsectionGrade
-from lms.djangoapps.grades.tasks import recalculate_subsection_grade_v3
+from lms.djangoapps.grades.tasks import recalculate_subsection_grade_v3, are_grades_frozen
 from opaque_keys import InvalidKeyError
 from opaque_keys.edx.keys import CourseKey, UsageKey
 from openedx.core.djangoapps.content.course_overviews.models import CourseOverview
@@ -704,6 +703,13 @@ class GradebookBulkUpdateView(GradeViewMixin, GenericAPIView):
         course and subsection grades for the specified user.
         """
         course_key = get_course_key(request, course_id)
+        if are_grades_frozen(course_key):
+            raise self.api_error(
+                status_code=status.HTTP_403_FORBIDDEN,
+                developer_message='Grades are frozen for this course.',
+                error_code='grades_frozen'
+            )
+
         course = get_course_with_access(request.user, 'staff', course_key, depth=None)
 
         result = []
diff --git a/lms/djangoapps/grades/tasks.py b/lms/djangoapps/grades/tasks.py
index 0b5e149c56..e7d7c1d471 100644
--- a/lms/djangoapps/grades/tasks.py
+++ b/lms/djangoapps/grades/tasks.py
@@ -60,7 +60,7 @@ def compute_all_grades_for_course(**kwargs):
         log.debug('Grades: ignoring policy change regrade due to waffle switch')
     else:
         course_key = CourseKey.from_string(kwargs.pop('course_key'))
-        if _are_grades_frozen(course_key):
+        if are_grades_frozen(course_key):
             log.info("Attempted compute_all_grades_for_course for course '%s', but grades are frozen.", course_key)
             return
         for course_key_string, offset, batch_size in _course_task_args(course_key=course_key, **kwargs):
@@ -115,7 +115,7 @@ def compute_grades_for_course(course_key, offset, batch_size, **kwargs):  # pyli
     offset.
     """
     course_key = CourseKey.from_string(course_key)
-    if _are_grades_frozen(course_key):
+    if are_grades_frozen(course_key):
         log.info("Attempted compute_grades_for_course for course '%s', but grades are frozen.", course_key)
         return
 
@@ -148,7 +148,7 @@ def recalculate_course_and_subsection_grades_for_user(self, **kwargs):  # pylint
 
     user = User.objects.get(id=user_id)
     course_key = CourseKey.from_string(course_key_str)
-    if _are_grades_frozen(course_key):
+    if are_grades_frozen(course_key):
         log.info(
             "Attempted recalculate_course_and_subsection_grades_for_user for course '%s', but grades are frozen.",
             course_key,
@@ -205,7 +205,7 @@ def _recalculate_subsection_grade(self, **kwargs):
     """
     try:
         course_key = CourseLocator.from_string(kwargs['course_id'])
-        if _are_grades_frozen(course_key):
+        if are_grades_frozen(course_key):
             log.info("Attempted _recalculate_subsection_grade for course '%s', but grades are frozen.", course_key)
             return
 
@@ -354,7 +354,7 @@ def _course_task_args(course_key, **kwargs):
         yield (six.text_type(course_key), offset, batch_size)
 
 
-def _are_grades_frozen(course_key):
+def are_grades_frozen(course_key):
     """ Returns whether grades are frozen for the given course. """
     if waffle_flags()[ENFORCE_FREEZE_GRADE_AFTER_COURSE_END].is_enabled(course_key):
         course = CourseOverview.get_from_id(course_key)