You can drop a score (or more than 1) per grading category, but you cannot choose the lowest from a set of categories.
1. Click on the cogwheel opposite the grading categories name:
Note My category was called “Window 1” you may have “;Window 1 quizzes” etc.
2. You’ll see a pull down menu; click on the pencil (Edit) icon:
3. You’ll see the dialog box below.
Notice that you can change the weighting of the category, in a edition to dropping a chosen number of lowest scores (or highest scores…).
If there are assignments whose score you do not wish to be dropped you can choose the scores you don’t want dropped by clicking the “Add an assignment” hyperlink after “Never Drop”: