How do i restrain myself from beating up a kid in school?

ok im 13 in the 7th grade and there is this black kid real scrawny in such and he keeps pushing me around and flirting with my girlfriend im trying to restrain myself because i don't want to get on probation and my girlfriend will break up with me if i do it and i iknow i can kick his cause i take MMA (Mixed Martial Arts) and i will ******* murder him im trying really hard not to punch him but its getting to that point where im just going to explode on his ***