In my ASU dojo, students are encouraged not to ask questions during class, but they sometimes do so anyway and usually get an answer. Questions after class are encouraged, although not actively so. My impression is that most of the question asking and answering happens during training with a sempai for kyu tests.
I always ask if anyone has any questions at the end of every class I teach. In Seidokan, my teacher asked for questions after every technique demonstration.