ucas predicted grades, law especially

hi i’m a black student and the only black student in my class just keep this in mind. and please try to read this 😭
i moved to a new school in january and i noticed my law teacher didn’t like me, he seemed to prefer other students over me which is fine as i am quieter than others and he tends to get on better with people who are more outspoken.
however for every assessment that we’ve been given i’ve gotten quite high grades either full marks or A and B’s. for both the y12 summer mock and y13 mock i’ve gotten full marks. so when it came to my predicted grade he gave me D, which makes no sense as i’ve never gotten a D.
what can i do as when i’ve spoken to him he’s been passive agressive accusing me of accusing him of making a mistake, he’s told me to do extra work which i’ve done already and when i’ve spoken to people higher up than him they haven’t taken it seriously? is there anything i can do

As above - go and talk to your Head of Sixth.

Can you make an appointment with the head of 6th form with your parents and bring all your grades so far.