To delete an assignment, go to your Assignments page for the assignment's class. Find the assignment you would like to delete and click the trash can icon (stacked dots if on mobile) in the top-right corner of the assignment.
Once you delete an assignment, you will not be able to recover that data. We recommend that teachers download data prior to deleting an assignment.
Please note: You will need to repeat this for every class you want to delete the assignment from. Then you can create the assignment again (and post to Google Classroom again if desired).
Are you a co-teacher for a class? You will not be able to delete an assignment as a co-teacher. Secondary teachers also cannot archive classes, delete classes, or remove a student from a class.