My teacher doesnt know how to teach!!!!!!!!!!! wt would u do if u were me?

i hav this math teacher and she cant teach at all!! no 1 understands anything when she teaches and everyone hates her. everyone tried complaining to the principal but she doesnt believe us we even told our parents and they complained to the school but nothing happened and some students even told her tht she cant teach rite in front of her face but nothin happened. i used to always get an A in math and im in 9th grade i never even got a B but when she started teaching me i got a C in math. i tried switching classes but it wasnt possible. i hav no idea about wt i shood do shes affecting my grade and i tried everything. If u were in the same situation wt would u do? or if it already happened 2 u tell me how u got through it