When I picked up my son (almost 3 yrs) at preschool today his teacher told me they were having a hard time with him. Said he was pushing and being mean to other kids and not listening to his teachers. Not that he is an angel but he is usually fairly well behaved at playdates and around other kids, at least when I am around. I was really shocked and not exactly sure what I should do. What am I supposed to do to make him behave while he is at school?