Back when I was in university, one of our teachers gave us a lecture about the importance of having your cellphone off (while I set mine to silent, I don't carry a watch, so I need it on, but I'd never answer it), someone's phone rang. The LOOK he gave him was *awesome*.

I just... pay attention in class. I also sit near the front because my vision is crap and chalkboards can be pain to read.

Of course, I haven't been inside a classroom for four years or more (distance education is joy, and I can raid in 'class' during our very rare chat sessions), so maybe I'm missing something.