Here is how to delete assignments:
Navigate to your Gradebook and select a class from the drop-down menu. Select the Pencil icon under the name of the assignment you want to delete.
Situation 1: the assignment to be deleted hasn't been started by students (no submissions, no grades).
In the Editing An Existing Assignment dialog box, click the Delete Assignment button.
Confirm your action by clicking the Confirm Deletion button in the Delete Assignment dialog box.
Situation 2: the assignment to be deleted has already been submitted by one or several students.
The deletion will also delete related grades and student submissions. Therefore, you have to explicitly confirm your action by entering the word DELETE before being able to validate the deletion.