I didn't make a habit of missing lectures as an undergraduate. In my first CS course, the instructor was so clearly teaching straight from the text (which he had written) and the material was so simple that four of us formed a consortium and took turns going to lecture just in case something out of the ordinary happened. Nothing ever did. But after that, even when instructors were less than effective (and I certainly had my share of those), I went to lecture. I would bring something useful to do. We didn't have wireless, let alone laptops or personal computers of any sort, in those days, so when I ran out of pencil-and-paper work, I read books. I got some great works of literature read in the back of MC classrooms.
The reason I continued to go is that even the worst lecturer usually managed to, now and then, illuminate some aspect of the topic, but I could never be sure when they'd actually do it. That our best lecturers get 70% attendance on some post-midterm days is a mystery to me. When I have an 8:30 class, a class in a distant building, or another section happens to be more convenient (one term going to the other section meant that students could just sit there and have their next instructor come in), my statistical expectation of attendance starts inching towards zero.
I could take this as discouraging, but in truth the lack of attendance doesn't bother me much. I know I'm not the only thing going on in students' lives. Having a small class would be advantageous if they all sat near the front and took advantage of the low attendance to make the class more interactive. But when they're sitting in their usual seats scattered through a hall capable of holding 120, the dynamic is much the same.
I tell students to bring something discreet to do if they want to sit in class and only pay partial attention. Once when I was teaching in a large amphitheatre, three students took that as a cue to sit way up at the back and play cards. I walked up, turned off my microphone, and told them that I didn't think I merited that sort of treatment. One came down to apologize afterwards, bringing a similar letter from another one. The third sent me a letter accusing me of hypocrisy and denouncing me for embarrassing him in front of the whole class. Go figure. --PR
(Adapted from a blog posting made November 7, 2003.)