[New series where first year university instructors give advice to high school teachers and future students. The following advice was based conversations with several lab instructors at the University of Waterloo.]
Many first year university students are surprised when they suffer the consequences of a missed deadline. With a class size of over 1,400 students, any kind of late-submission penalty can be difficult to administer. So if it's late — even by a few minutes — it's a zero. End of story.
Students need to get their graded labs returned in a timely fashion; we don't have the luxury of waiting for everyone to submit his or her work.
So tell your students: deadlines matter.