Education Code § 17535
ARTICLE 9. Joint Use
(a) Except as provided in subdivision (b), no agreement entered into by a school district pursuant to this article shall rent or lease vacant classrooms or other space in operating schools for less than fair market rental for comparable facilities.
(b) A district may enter into an agreement to rent or lease vacant classrooms or other space in operating schools to public entities for less than fair market rental for comparable facilities.