A process carried out by university administrators in the Autumn term which involves shedding students who don't turn up regularly to classes to ensure they aren't charged fees and become an unnecessary financial burden to the institution. This is performed by the student being summarily "deregistered" on the grounds that they are "inadequately engaged" on their programme of study. As a result, students find they are suddenly unable to submit coursework or access any university facilities whatsoever, thus providing proof that they are indeed no longer engaged.
Chris the student: Hey professor! Why can't I submit coursework or access any online library facilities in order to complete my term papers?
Professor: You've probably become an unwitting victim of the most recent "Autumn Courtesy Flush."
Chris: What's that?
Professor: You've been deregistered because you haven't been coming to class.
Chris: My God! But if I can't submit assignments I'll fail the year.
Professor: Yes, well you should have thought of that, shouldn't you? Anyway, good luck with your career.