What's done, is done. My husband and a friend switched papers once in high school to prove a point. You see, my husband was captain of the football team and this one teacher graded his papers with prejudice. They told what they did voluntarily after they were graded. My husband's paper was an "A" with his friend's name on it. The friend, an "A" student, got a "C" with my husband's name on it. They, of course, both got into trouble, but the principal personally made sure that the teacher's grading was fair afterward. In this case, my husband's parents did not believe their son, so he felt he had to prove the point to all the adults involved. If I were the parent and believed my child, I would be having some parent-teacher conferences and involving the principal if it was not resolved.
Another great case study that demonstrates that no one cares about children more than the parents and that no one is more qualified and inspired to teach children than the parents. This is something home schooling parents have known from the very beginning.