High School's grading errors and transcript

Hi, my son has recently submitted his application and we have discovered that his Calculus teacher may have graded some of his fall term tests incorrectly, i.e. giving him different point totals than other students on identical questions. In addition, he is entitled to extra time on his tests for a vision issue, and this teacher also failed to handle that correctly. His grade moved from an A to a C during this period of time. He would like to drop the class and take it independently, but we would like the school to acknowledge the possible errors when they remove the class as we presume the schools he applied to would be notified of the curriculum change, and obviously the C has damaged his GPA. Do you have any insight as to how universities would view this change?
Thanks so much!