Thing about art class (I've taken a lot of them) is that serious artists don't give a fuck what you look like. They may say to themselves "great body!" or "whoa, dude has big balls!" or "that's a dumb tattoo," but what they really notice is whether you're a GOOD MODEL. Hold a pose without moving around, choose poses that are interesting/challenging to paint and draw, etc. So this is a good environment for someone who isn't that confident - you're being judged more on your skill as a model, and less as a "hot chick" or whatever. Good for them.