At the moment, I am going over the first draft of my next book, which has been copiously marked up with red pen by the editor. The following thought occurred to me (during my ninth hour of looking over the proposed edits):
Many teachers fill student papers with editorial marks and corrections, indicating that a certain word should be capitalized, or that a comma is needed, or that a certain sentence is awkward or needs to be rephrased.
However, there is no point in putting editorial marks on student work if the student is not asked to go back and fix them. If the teacher does not require corrections should be made and the work resubmitted, it is a waste of time to point out how things ought to be different.