[EricH]

At my college, it's pretty much anywhere anytime, unless you are in class. Some profs will simply make a comment ("musical interlude"), but others...

Two of my profs have had a "rule": If your phone goes off in class, you bring goodies the next time, for the entire class. So far, no one has brought goodies while I was in class.

My high school says "not during class". I can't remember when they are allowed, mainly because I didn't have one.