Ok so I’m not a parent and I wont be for a while. Why take my advice then? I’ll tell you why, because I’ve been in your sons shoes, he was me. I am now 17 and I can tell you that the most effective form of punishment is saying to your son that you know he’s better than that. When I was your sons age I had great grades and the same behavioral issues. Having your parents tell you that you are better than that, and saying (to your son) that they have so much potential and that you are concerned for them not only gives them hope but it also wakes them up. It worked for me, it scared me into straightening up. I hope you acknowledge my input because I was your son and I know how hard it can be for both you and your son.