His behavior may improve for a few days, but then he slips again. His grades are good. As a few Bs. He's bright and outgoing with a good personality. You and the teacher need to put your heads together to devise a plan for handling this situation.
Many teachers tape a piece of paper divided into time periods on the child's desk.
The key to helping with this issue is consistently dealing with the problem and providing immediate consequences and rewards. Decide with the teacher in advance how many checks are needed to make it a good day, and ask the teacher to send home each day a note or message in your son's planner. Then follow up at home. Three out of five good days in a week could mean extra computer or TV time or having a friend over to spend the night. Less than three out of five good days could mean not going to a special event over the weekend.