When I taught math, I had a sure-fire cure for this.
Every class started with a 10-minute "question and answer" period. The rule was that someone would ask questions and someone would answer. The unstated rule was that you really, really didn't want me asking questions. They only made that mistake once. ;-)
This may only work in a class which is small enough that every member has a realistic fear of being picked to answer a random question from the previous day's class.
This worked really well with cumulative homework sets. In homework people kept on being reminded of things that they didn't quite get earlier in the course, and since they were looking for things to ask me anyways...