The boy is challenging us

Since spring break, the boy has had more bad days than good days with his behavior at school. It is not just school, but he's testing his baseball coach, his swimming instructor, and especially us. Nothing significant has changed in our lives and we can not figure out why he is having more problems than usual controlling himself. If he is good at school, he gets to watch tv in the evening and can have candy. 3 good days in a row and he gets to go to Chuck E Cheese. If he misbehaves, no tv, no candy, and he does not get to sleep with his bear lovey. Last night, he was forced to delete his favorite cartoons from the Tivo. Tonight, he will have to throw all of his candy away if he misbehaves at school. One more really bad day at school and he doesn't get to go on the school field trip to the zoo. He'll miss out on a birthday party this weekend as well.

I emailed his teacher and she sent back good suggestions, but we are already enforcing them all. I am completely frustrated and at a loss for how to fix this problem.