I’m always puzzled by students who habitually miss class. I don’t mean the students who are facing serious challenges of one type or another, I mean the ones who wake up and decide, “Nah.” The student – or someone – has forked over a lot of money in tuition and fees and, if for no other reason than that it demonstrates sloppy handling of investments, it seems silly to me to skip out.

He looks so sad.
People are a diverse lot of course and the flipside is also true: I have students who drag their nearly-dead selves into class when they are sick and should absolutely not be there. But it’s the former I can’t figure out. They could be there and they should be there and it’s well established that missing classes can reduce your grade. I’ve often wondered though, how much can one miss before one’s grades begin to suffer?
It depends, obviously. Miss a day in one of my classes and you can make it up without difficulty. Daydream for 5 minutes in a differential calculus class and your entire semester could be doomed.
Just focusing on one of my classes then, I did some back-of-the-napkin figuring. This class meets just two days a week, on Tuesdays and Thursdays for 75 minutes. I have a couple of excused absences built into the grading scheme, to accommodate the aforementioned students who might have to miss from being sick or getting a flat tire or had trouble arranging child care, etc. There are a couple of other meetings that are taken up with exams. All told, there are 26 unexcused meetings of the class for which testable material will be covered. So once a student has used up excused absences, how many more can they miss before they’re likely to drop a letter grade in the course?
I think it works out a bit like this. To earn an A, one must grasp at least 90% of the material covered. With each unexcused absence, however, the student is missing incrementally more and more of the course content. Mastering 90% of 75% of the material does not produce the same outcome as mastering 90% of 100% of the material. Thus, with all matter of caveats and assumptions about linear relationships, equal amounts of course material provided per lecture, etc. it looks like missing even one more than the two excused absences in my course could be enough to drop an A student to a B. Missing two or three (so four to five total absences) almost certainly costs a full letter grade. Those habitual truants, i.e., people who might wrack up four or five unexcused absences? Even their most diligent efforts will likely relegate them to grades of C or lower. The good news is that this problem is readily corrected by the simple act of walking through the door. Go to class!