Please be careful. You might think that you want Delete an assessment from a class. You don't. You want to Unassign an assessment from a class. Delete means delete.
Click here to Unassign an assessment from one or more classes.
Ok, so how do you DELETE an assessment?
1. Navigate to the Library tab. Click on the assessment that you want to delete.
2. Click delete.
3. Type "DELETE" and then click the "Yes, Delete" button.