I create quizzes which draw 25 questions at random from a bank of 100 questions. I leave quizzes open to students after the due date to allow them to study for exams. But when they re-take quizzes after the due date, the new grade is counted, although designated as late. My solution is to require a password to take the quiz after the due date. Is there any way to retroactively grade the quizzes taken up to this point to eliminate the grades for quizzes taken after the due date? .