I can answer that one for you having recently taught a semester of postgraduate database systems to a cohort of just 6 students. It was a blast. I followed a

I can answer that one for you having recently taught a semester of postgraduate database systems to a cohort of just 6 students. It was a blast. I followed a pre-planned course of lectures, but due to the low class sizes it didn't work out that way a lot of the time. An example, following a question about relations, I ended up doing a chalk n' talk on set theory and explained how set theory could be represented as first-order logic. Filled the wall full of Greek letters and drilled down into the topic. Then started talking about axioms. The students joined in - you could see them taking an interest, as the conversation had turned. In the event we spent 90 minutes (it was a 60 minute session) working through axiomatic set theory on the board. I had to look things up as we went. It was great, the students learned a ton (and some of the content turned up in their assignments, too) - I learned a fair bit, as Feynman will attest, there's nothing like teaching a topic to make you understand it better yourself - and it was productive and interesting. I'm not sure I could repeat the same trick with a cohort of 20 or 30.