Dealing with teasing

Hi sisters

I have a question on, I guess bullying, but on a very lighter degree. My 9 yr old son will get teased. But only because he gives them the reaction they want. He does tell the teacher about some things but doesn't want to go to her all the time. I'm wondering if anyone has any tactics to help him calm himself and walk away instead of getting angry and yelling at them because that's what they want.