In my "Introduction to Computer Science" class at Carnegie Mellon, I stopped going after the first week since it was really basic stuff I already knew, all the lessons/notes were on our network and all assignments could be turned in electronically.
When I showed up for the final (the only in-class test), the prof & I had this exchange while he was proctoring:
P: Excuse me, are you in this class?
M: Yeah, I'm [DWray]. (Showed my ID.)
P: Really? Wow, I have some papers for you.
Class: ((Laughs))
Got an A. But I wasn't so lucky in the real CS classes. I hate LISP...