As someone who stutters hardly and ruined their social life with this I actually don't know. I never got helped by teachers or something. You should definitely go to his teacher and maybe(This can be hard for your son) let your son tell it in the whole class. What kind of stuttering does he have? You can read what I have here> https://www.reddit.com/r/Stutter/comments/93iv4a/my_inner_mind_stuttering