Cal. Educ. Code § 5025

If an election is called or a resolution of the county committee approving a proposal to establish trustee areas is adopted, as applicable, pursuant to Section 5020, the county superintendent of schools having jurisdiction shall, as to each trustee area having more than its allotted number of representatives in the membership of the governing board for the next succeeding school year, determine by lot which of said representatives shall relinquish their offices either immediately upon the election and qualification of the governing board members who are elected as provided in Section 5024 or on the first day of April next succeeding the election or the adoption of the resolution, as applicable, establishing trustee areas in the district, whichever is the later.