To find where the Letter Grade scale is being used, run the Gradebook Parameters - By Section report. You can do this in any product by:
  1. Select Analysis > Reports
  2. In Report Search, type Gradebook Parameters
  3. Click Find
  4. Click Run
Once you find where the Letter Grade Scale is being used, you will need to remove the Letter Grade Scale from the Gradebooks where it is being used. As the teacher:
  1. Select Classes
  2. Choose the Class that is using the Letter Grade Scale
  3. Select Gradebook
  4. Click Edit Setup
  5. Under Letter Grade Scale, click the Drop-Down menu that has the scale
  6. Change it to the blank option
  7. Click Save & Close
Note: If the Letter Grade Scale is grayed out, the teacher will need to un-publish any assignments using that assignment type. This can be done by editing the assignment, un-mark Add to Gradebook and click Save.

Lastly, once the Letter Grade Scale is no longer tied to any Gradebooks you can delete by going to Academics:
  1. Select Grades > Grading Setup > Gradebook Settings 
  2. Scroll down to the Letter Grade Scales section
  3. Click the 3-dot button to the left of the letter grade scale you wish to delete
  4. Click Delete Scale