It's Started

This is the third time that Sid has come home from daycare with some sort of damage to his face. And each and every time it's happened there is one name always associated with the injury. Let's just call her Ash, shall we. Apparently, this girl was really wild when she first started attending Sid's daycare. She didn't care who she hurt or scratched as long as she got her way. Supposedly she has calmed down a lot since then. I don't know. I just want her to stop messing with my boy. According to one of the teachers I spoke to today, she observed an interesting phenomenon: Ash got jealous and upset because Sid was paying attention to another more mild-mannered girl. Sid, being the laid back, protective, gentleman that he is, he never fights back. How can I teach him it's ok to be assertive and protect yourself without necessarily fighting back??