You're in highschool. Ask your peers questions about the assignments if you don't understand something. A teacher can't fail you, you fail yourself. You turn in homework, she grades it, and then you get it back with your grade-same with tests. You keep them for records in a folder and at the end of the semester you can figure your own grade. If the grade she gives you don't match yours, you got your proof.
Not sure how much longer until the end of your semester, but if it's close to the beginning, just ask the principal to transfer to another teacher. It's all the same curriculum.
