California Code, Education Code - EDC § 60045

(a) All instructional materials adopted by any governing board for use in the schools shall be, to the satisfaction of the governing board, accurate, objective, and current and suited to the needs and comprehension of pupils at their respective grade levels.

(b) With the exception of literature and tradebooks, all instructional materials adopted by any governing board for use in schools shall use proper grammar and spelling. The state board may adopt regulations that provide for other allowable exceptions to this subdivision for educational purposes, as determined by the state board.