Help me help my child with overstimulation and stimming

My son started kindergarten this year and so far not a bad experience. He has a SE teacher in his class and a case manager at the school. No complaints about the system.

He came home yesterday and said some kids were being mean to him at lunch for his arm waving and flapping. He does it when he's excited or overstimulated.

Kids are kids and he's going to have to learn to deal with other people. Having said that, is there anything I can do as a parent to help him with his stemming?

I also don't think he fully understands when kids are being mean to him so it might be better or worse with how bad they are teasing him. Anything I can do or say to help him understand?