California Code, Education Code - EDC § 49066

(a) When grades are given for any course of instruction taught in a school district, the grade given to each pupil shall be the grade determined by the teacher of the course and the determination of the pupil's grade by the teacher, in the absence of clerical or mechanical mistake, fraud, bad faith, or incompetency, shall be final.

(b) The governing board of the school district and the superintendent of such district shall not order a pupil's grade to be changed unless the teacher who determined such grade is, to the extent practicable, given an opportunity to state orally, in writing, or both, the reasons for which such grade was given and is, to the extent practicable, included in all discussions relating to the changing of such grade.

(c) No grade of a pupil participating in a physical education class, however, may be adversely affected due to the fact that the pupil does not wear standardized physical education apparel where the failure to wear such apparel arises from circumstances beyond the control of the pupil.