This is a tough one. I don't know where you live, but in california they have a long drawn out way to help parents diagnose and place their child. It is up to the parent to talk with and innitiate any actions that the schools can help them with.
The other problem is that at that age there can be many issues, including just an over active child. So one needs to take these steps carefully in order not to mistakenly label a healthy child with a disability.
As a substitute teacher I have seen many children and some I "think" may need some kind of extra attention. But I also see many that just need a firm swat on the bum and a firm talking to by their parent. So keep an eye on your son and ask his teacher for some info that may help you find the right path to take. My prayers are with you guys.