Having a serious problem with my brother's geometry teacher. What to do?

My brother is failing his geometry cl because the teacher is a blatant racist towards chinese people ( we are chinese ) and says remarks that are seriously affecting my brother's performance in cl. My brother at this point has no motivation to even try and i don't know if i should talk to the math director of my school to have her deal with this teacher or not. He is an old teacher of the school so it's not like they're gonna fire him and the math director has yelled at him before but not over race. It also turns out that the tests that my brother is failing at is Triginometry tests. This guy is a Geometry teacher and my brother is in the 10th grade. He won't be learning Trig or FST until the 12th grade. Is he even supposed to teach this? I know i need to talk to someone; either the teacher, guidance, the deans, or the math director of our school but who do i turn to and what do i do? I really need help on this one. I want my bro to go to college.