You might wish to drop the lowest grade out of a series of items for each student. For example, dropping the lowest quiz grade out of a set of 9 quizzes. You can set up your gradebook so that this is done automatically.
There are several of conditions that must be met:
If you do drop the lowest grade(s) we recommend showing the Calculated Weight (Weightings) column in the User Report as this displays to students which items have been dropped. By default that column is visible, so as long as you haven't hidden the column students will see it.
The grade item that is dropped will be indicated in the Calculated Weight column in the User Report (visible by default) for both students and the instructor.