11 year old - brushing his teeth!!?

Three times a day seems a bit excessive for a kid but I don't think you are going overboard about brushing. It is important that he starts the habit at a young age. Obviously, if his mom had made him do it when he was little then it probably wouldn't be a problem now. I agree that charts are too young for him. Unfortunately, you will just have to be on his back until he does it. Make sure it is part of his "getting ready in the morning" and "getting ready for bed" routine. If you ask him every time and make him stop what he is doing to brush his teeth, I think he will catch on pretty quickly.