- Navigate to Lists > Manage Lists
- Click the Manage basic and advanced lists block under List Actions
- Click the List Templates tab
- Select Category: Grading
- View/Copy the list "Current Year Academic Grade Detail"
On the Selected Objects tab:
- Select Assessment Grade and click Assessment Grade Plan Grade
- Still under Assessment Grade, click Assessment Grade
On the Display Fields tab:
- Click Select Fields
- Expand User Base > Course Enrollment > Enrollment Grade > Assessment Grade Plan Grade
- Mark Grade Description
You can then remove these grades and should then be able to delete the assessment grade plan once all those grades are removed from it.