You can delete a grading scheme in your Account Settings.
Note: If you delete an account-level grading scheme that has been enabled at the course level, the grading scheme will not be deleted from the course.
Select the Managed Account in the Courses & Groups drop-down menu.
In Account Navigation, click the Grading link.
Delete Grading Scheme
Locate the grading scheme you want to delete and click the Delete icon.
Click the Delete button to delete the Grading Scheme or the Cancel button to not delete it.