I’m so sorry for your son. My heart breaks when I hear about things like that. Pray to St. Raphael (you can find a novena online). He is the patron saint of happy meetings. I met my husband after saying a novena to him, but he is not just for finding future spouses. I’m sure he would help your son find a friend!
Do you know why your son is being left out? Sometimes kids are just mean for no reason, but maybe there’s something you can do to help him if you know why he’s being ostrasized. Good luck! I’ll say a prayer for him as well!