Whiteboard discussion of U2 WS4. With so many students (35), I've found that the best practice is giving each group 3-4 problems to whiteboard so that the entire worksheet is covered, with (hopefully) a little overlap. Rather than go over each board independently, I let students spend ~10 minutes walking around the room checking boards, taking notes and asking questions. Then we'll spend 10-15 mins as a group answering any lingering questions.
This works pretty well in my honors classes because most of the class will arrive having completed (or at least attempted) the homework. In my regular class, so many kids never attempt the practice, that we'd spend all hour just trying to whiteboard the problems and even then it would really only be 4-5 kids doing the work. Then the discussion is pointless, because the students who don't participate simply copy the work off the boards thinking that will be sufficient (which is obviously isn't).
At it's best, I love this idea. It's dynamic - it gets the kids working together, moving around, and holding them responsible for seeking help. With an efficient class, we're easily doing 3-4 distinct things in a single class period which helps the day seem shorter.
At it's worst, this strategy only benefits the kids who take it seriously. Of course, that's true with most methodologies but sometimes I fear what students are telling parents who don't understand the modeling philosophy, especially when there aren't any pre-printed notes or a useful textbook to supplant the classroom environment.