Does your son have an I.E.P.?
If he does not, and I.E.P. is a plan (Individualized Educational Plan) that you and the school staff put together that helps him succeed. If your son has some kind of official autism spectrum diagnosis by a doctor, then he qualifies for an I.E.P.
In an I.E.P., you can ask for things like preferential seating at the front of the class, time-outs for when he has sensory overloads, more time on tests, or test-taking in a different location. You can also get school-related speech therapy and occupational therapy.
I'm sure other people will come up with recommendations as well.
Kris