My parents always treated it like it was nothing. I've visited many psychiatrists and speech therapists, even though it didn't help that much. Just don't be patient with him, he doesn't need to feel bad for stuttering, make him understand that. School might be hard for him, littles classmates can be very rude, much more than adults, so at least it should be good for him at home. In my personal experience, stuttering was very hard during primary and middle school, after that you learn how to live with it, and also you don't have to endure the mockeries of your classmates.