Teen Getting Poor Grades & Being Suspended

Question:

I attended your lecture on Positive Discipline held at Mira Costa on the 21st, because I really need help on where to go from here. I have an almost 13 year old boy who is testing his limits (and mine). What would be the best approach for me in the following instances:

He was getting poor grades in two of his classes so I said until the grades are back up to an acceptable grade he was grounded from everything! Obviously this was before your lecture. Just as he gets A’s on the next two tests (after just one week) he gets a detention at school for spitting a spit wad. Now I am really showing my disappointment, but let him have his life back. The following week he gets another detention for misusing the computers in the library. At this point he just knows how disappointed his father and I are. That same night he is at a friend’s and the four friends get into mischief by damaging the neighbors property. On all the occasions he said he did things even though he knew they were wrong but he didn’t want his friends to think he was weak and didn’t want to be seen as NOT COOL. How should I handle this kind of stuff? Please help. Beth