If it helps at all, I’m currently 16 in secondary school with a stutter. It’s not the worst stutter in the world but it’s still not good either. I have been laughed at before, it happens, but not as much as you might think. I’ve never been bullied and I’ve found that kids are actually a lot more understanding than people think. They never really do anything like mock me or anything like that and most of the time they just wait for you to say what you want to say even if it takes a few seconds. I have plenty of friends and none of them really care about the way I speak. Honestly, your son should still have a pretty normal life even with a severe stutter