Cal. Education Code § 45110

Classified employees shall not be required to perform duties which are not fixed and prescribed for the position by the governing board in accordance with Section 45109, unless the duties reasonably relate to those fixed for the position by the board, for any period of time which exceeds five working days within a 15-calendar-day period except as authorized herein. An employee may be required to perform duties inconsistent with those assigned to the position by the governing board for a period of more than five working days provided that his salary is adjusted upward for the entire period he is required to work out of classification and in such amounts as will reasonably reflect the duties required to be performed outside his normal assigned duties. Notwithstanding the provisions of this section, a personnel commission and governing board, or a governing board in a nonmerit system district, may, by written rule, provide for an upward salary adjustment for any classified employee required to work out of classification for any period of time less than that required herein. It is the intent of this section to permit school districts to temporarily work employees outside of their normal duties but in so doing to require that some additional compensation be provided the employee during such temporary assignments. This section shall apply to districts that have adopted the merit system in the same manner and effect as if it were a part of Article 6 (commencing with Section 45240) of this chapter.