Go to "Site administration > Grades > Grade category settings" and select all of the available aggregation types. Go to the gradebook in a course. Create (important that you create and not edit) a manual grade item under a category that uses the following aggregation types: natural - should display Extra credit enabled Weighted Mean of Grades - should display Item weight Simple weighted mean of grades - should display extra credit Mean of grades (with extra credits) - should display Extra credit weight Other aggregation methods shouldn't show an extra credit box as enabled . If in doubt edit the manual grade item and view the parent category (if it exists) to confirm.