Cal. Educ. Code § 44972

Where one governing board serves as the governing board of two or more separate districts, an employee may fulfill the service requirements provided in Section 44967 or in 44969, or both, by service in any one or more of the districts under the jurisdiction of such governing board. At the option of the governing board the provisions of this section may apply in whole or in part to service rendered prior to October 1, 1949.