My kid tries telling me the math teacher is horrible etc. I tell her okay so rather than complain how can you still do well. Personally I like the teacher but I agree the current teaching method the school is using is not a good fit for my daughter. That doesn’t mean it is an excuse not to do well. Most of the time they are given a packet of work with one or two examples and can work as a group. The teacher doesn’t do things the old way of standing at the blackboard and writing examples step by step (may be old fashioned but would work better for my daughter).
My daughter has done a mix of things to help. For instance she is part of a group chat that works together to answer occasional harder homework problems (no idea if it helps I’ve never seen the chat), talks to friends in the same math class other periods or have other teachers etc. My daughter knows she can go to free after school help though she refuses. She knows she can look up similar math problems on things like khan academy, try to redo an example problem to see if it helps etc. She isn’t the top student but does well enough to stay in honors and managed to get a 100 on the midterm even with her horrible teacher.
I’m not sure who the supervisor is. If it is the math department leader they probably go by the teacher unless they can verify an true issue. If it is the principal at least here they don’t get involved with grades (unless it is an issue of gross misconduct vs struggling student). The school committee would also not have any involvement in student placement.