Ask the school to evaluate him. It is free, and by law, they are required to do so with a written request.
You can use this sample letter and give it to your son's principal, special education admin at your school, and the special admin director for the whole school district. (make sure the latter is sent registered mail, with return receipt)
http://www.adhd-add.info/sampleletter.html
Once you submit that letter, they are on a scheduled timeline for the evaluation, by law.
You may gain some real insights into what may be going on with your son, and support services at school if he qualifies. Even if he doesn't - you'll have some idea of where to begin on your own.