How do I add or delete grades/results for a pupil?

Make sure that you're using the series that you need to remove the grades from.

Go to Admin > Edit Results

If you are adding a grade/result, find the pupil on the left and look across the subject columns. Click on the relevant cell and use the dropdown menu to select a grade. 

If you are removing a grade/result, click on the relevant grade and use the dropdown menu to select the 'blank' value.