I find that if the rules are laid out in the beginning of the term, the majority of the students will adhere to theses rules. Although, there always seems to be one who tries to buck the "system". As the instuctor, how you deal with that student, sets the tone for the rest of the terms. I have handld this incorrectly and paid for it and I have handled it well and all went well after. The most amazing thing happens when you handle it well. The other students in the class, seeing how you react and care about teaching them, will tend to take on the role of disciplinarian. I have seen proactive students handle the "problem" before I even have a chance to say anything. It truly is amazing to see.