One kid is making the other kids behave badly? How do you bring it up to the parents?

Speak to someone in authority at the church. Never tell a parent their child is less than perfect because they simply wont believe you. You didnt really think anything you could say would change things except to make them mad at you , did you? I think that is the problem with exposing well behaved children like yours to a situation like that. I would truly think twice about continuing to let your son witness it and I would either not take him, go elsewhere or to a different time service.