My Introduction to Computers for Arts and Social Sciences course usually has several hundred students when taught in the fall and winter (when I'm not teaching), but under 100 when I teach in the summer. So far I've had about 50 show up to each class. I'm finding this to be an ideal number when trying to engage the students in in-class discussion.
Even with a large group, I could definitely imagine doing a couple of the discussion exercises I've done with my students. For example, I recently did a "mock quiz" where I made up some questions on the programming concepts we talked about in class and got students to write their answers as best they could. Then I told them to discuss their answers with their neighbour(s) to find out where they needed to enhance their understanding.
The next step I took was to ask a few brave students to share their answers with the class. They did, and we corrected their understanding as needed. But then something interesting happened. Students felt comfortable asking more questions on the same topic, getting deeper and deeper and uncovering some really good points and clearing up some misconceptions I never would have known about otherwise. I was really impressed with the quality of the discussion that happened and know that it really helped the students as well.
I'm not convinced this would have happened in a room with 300+ students. Even being able to hear their questions or answers in a huge lecture hall would have been a struggle, and if my own experience is anything to go on, it's pretty intimidating to speak in front of that many fellow students. If we hadn't got past the "check with your neighbour" stage, I'm pretty sure there would have been many misconceptions still out there.
To me, this experience (among other similar ones) has really shown to me how valuable smaller class sizes can be, especially when teaching more technical topics.
What has your experience been? What kind of success have you had with questions and discussions in large lectures? Have you mostly had to stick to the lecture style and make it all one way?