Hah, the highest grade I ever got in a physics mock is an E. Good thing my teacher didn't pay too much attention to that because I got an A in every exam. It would be one thing if you were getting Ds, but you're not
Get your parents to complain. Loudly. My dad is a teacher and he has always told me that rightly or wrongly people who kick up a fuss tend to get what they want. Schools don't want to deal with drama and conflict, and are likely to change your predictions just to get you off their back.