I have a daughter who attends a preschool that runs an after school facility for 2 boys with 2 children of the owner. All 4 boys attend same elementary public school as my son. For short they know each other, but they're a year older than him.  For some time, they were playing nicely when my son comes by while waiting for me to pick up his sister.  Recently I noticed that they were treating him rudely such as not letting him play with them by running away from him/locking door to leave him out of the room/telling him his not part of family.  The elusiveness looks like they're allergic to him.  He took it meanly and has cried about it. I told him to let the director (who is the mom of 2 boys) know.  He did, but seems like not helping much.  What should I do?  Is it time to step in?  How? and what should I say?  Please help.