You might try to give each student their own random quiz to check and see if they watched everything. It can be done by making a question bank for the Lesson module. That is how I do it and you can even put a time limit on the random quiz so they don't have time to go back and "look up" the answers. I find that about ten question makes sharing answers/information too much trouble for them to remember and worthless because each student gets their own set of questions in a random order.