Deleting an assessment draft will not remove assigned copies of that assessment. If you would like to remove an assigned and/or graded assessment, you'll want to unassign the assessment, rather than delete it. Check out this article to see how to unassign an assessment.
Delete an Assessment Draft
Step 1: Navigate to your Draft Assessments section.
Step 2: Click on the ellipses to the right of the desired assessment.
Step 3: Select Delete.
Again, please consider the permanent deletion of the data and assessment before deleting an assessment.
Step 4: Select Delete to confirm.
What Happens When You Delete a Draft Assessment?
Grades in the Gradebook
All grades (points and standards) will remain in the gradebook if an assessment is deleted. If you want to remove the grades, you'll need to unassign the assessment.
The assessment will remain assigned to classes after the assessment draft is deleted.
You will no longer be able to use or assign that draft assessment. It is permanently removed from your account.