The largest class I've had so far for college math is seven students! One way I promote discussion is to put them in groups of 3 or 4 students and have them work a problem set together with the following rules:
1) Put your name on your own paper.
2) Complete the first problem on your own paper. When finished put your pencil down and wait for everyone in the group to finish.
3) Once everyone has finished, compare answers. If there is disagreement, work together to resolve the differences, clarify understanding, and decide on a final method to solve the problem. If a consensus cannot be met after discussion, a group spokesperson may signal the instructor for involvment in the discussion. Everyone then completes the problem and initials it.
4) Pass your paper to the person on your left. Complete the next problem on the paper handed to you. Repeat steps 2 - 4 until all problems are complete or time is up.
5) Retrieve your own paper when finished so you have a completed set of problems for reference or study.
This method not only promotes discussion, students cannot work ahead (thus isolating themselves from the group) because they must wait to do the next problem on the paper that will be passed to them. Better/faster students can assist struggling students if they choose to and conversely, struggling students can ask a member of the group for help or choose to wait until the discussion. Students love this method of problem solving and find it non-threatening.
