Adults usually see this as a discipline problem and sometimes it is. But it is usually a sign of learning problems. Think about your child's behavior. Now ask yourself this question. Have you ever seen a child who is doing well in school act like this on any regular basis?
Here is the typical argument. If he just settles down and behaves, he will do better in school. Here is the more important point. If he does better in school, he will behave better. Most always, the learning problem comes first and the behavior problem last.
Why does he misbehave? He may have a behavior disorder needing special treatment. This is so likely, it always needs checked out. Even if he does not have a behavior disorder, it is nearly certain he has a serious learning problem.
Just getting on him and pushing him to do better can cause him more problems than he already has. This is a good rule-of- thumb. Until you understand your child's problems, do not try to fix them.