Talk with your son's teacher and ask him or her to help you focus attention on your son's positive behaviors. Decide on one or two behaviors to start with (not hitting others, perhaps) and ask the teacher to send you a daily note to let you know how your son's day went, then follow up at home. A good day can earn an extra bedtime story or a walk around the block just with you; two or three good days in a week can earn having a friend over to play on the weekend. You can increase the amount of time required to earn a reward as your son's behavior improves.

As you've seen, it's difficult for some people to admit they've done something wrong. Be sure to model this behavior for your son by admitting when you've made a mistake, and follow the positive system I've just described by rewarding him with your attention when he admits to something he's done.

Since your son's behaviors appear to have been going on for awhile, you may want to get some additional help for him. Talk with the school counselor; he may be able to give your son some individual time or include him in a small group on good behavior. If you decide to get assistance for him outside the school, the school counselor or your pediatrician can refer you to a therapist in your community.