In order to adjust grades, Moodle allows the option to drop the lowest score from a group of graded assignments.
1. On your main course page in the Administration block on the left hand side, click Grades.
2. This will take you to the Grader Report page. Go to the Administration block on the left hand side and click Set Up. In the drop-down menu, click Categories and items.
3. The Categories and Items page should appear. In the Actions column, click on the Edit drop-down menu for the Category from which you wish to drop lowest grades and select Edit Settings. (If you haven’t organized your gradebook with items in discrete categories, but would like to do so, see the tutorial on Gradebook Setup.)
4. In the Grade category section, click Show more, and type “1” (or whatever number of grades you wish to) next to Drop the lowest. When you are finished click Save changes on the bottom of the page.