Hi Anon,
Start focusing on his positive behavior and rewarding only that. I do not know specifics, nor your or your son (family dynamics and what not) but try a positive behavior reward chart.
What I have done with my 7 yr old when he got a white slip at school I took everything (I mean TV, video games, movies, computer-his most prized possessions) away from him. Except for after school sports kids need an outlet, and I only took/take that away from him when he does not finish his homework.
In a calm and collected voice, I told him that he will have to earn everything back and that was the only reason why he had it in the first place. My son needed to grasp
responsibility, because obviously I did not instill that concept in him. By using a
positive outlook on my son's behavior, it did wonders. I stopped punishment and negatively reinforcing him until he understood that he needs to earn all the
fun stuff. Just like mommy and daddy work.
This is the 'gist' of what I did with my son:
I used a 'chore chart' as a reward chard. I wrote down the positive behaviors I wanted to see (i.e.good weekly progress report from teacher, manners, cleaning up after himself, keeping his room tidy-fixing his bed, picking up toys) him accomplish . I needed to remind him, "gee, that room used to be super clean, I wonder if I could hire someone to keep that room clean since NAME isn't. I bet the person I hired would love a new T.V..."
Yes, it's a minor threat (but i am not really going to hire or give his tv away) but it reminded him about his responsibility to keep his room clean. Later on that week, as I saw the room staying clean I would commend him on keeping it that way. Now, remember my expectations of how clean I want his room to be are rarely going to be met...at first...
I cleaned his room with him in the beginning to show him how I wanted it kept and of course it was not kept that way for too long. But the bed was fixed and the floor was clear of any toys and that was what he remembered.
I would give him a sticker/check/x on his chart if I saw him using his manners, cleaning his room, finish his homework, reading, ect. If he would begin to 'act up' I would remove checks/stickers/xs and remind him that that behavior was unacceptable. I would not negotiate with him, explain why I removed the sticker, I just say something along the lines 'awe bummer, looks like u just lost an X for
name the unwanted behavior. We can try again to earn it back though, but that
behavior was
unacceptable."
I used to be a behavior consultant for children with special needs, I am now an intensive behavioral support assistant. A lot of the ideas I use were from my training, however the show SuperNanny has been quite influential too.

) Good luck and remember
consistency and
positive behaviors are our friends.

You can also tweak my example more to fit your son's needs. Hope everything works out.