Some teachers would like the ability to set a date for when to drop the lowest assignment grade(s) in a class. If a teacher sets this up in the grade book from the beginning of the grading period, then a student's grade could continuously be fluctuating. However, if a teacher can set a certain date to drop those low grades, then it's only done once and shows a more accurate grade longer. This may also help teachers who forget to set this up when it's time for report cards.