California Code, Education Code - EDC § 5021

(a) If a proposal for the establishment of trustee areas formulated under Sections 5019 and 5020 is approved by a majority of the voters voting at the election, or by the county committee on school district organization when no election is required, any affected incumbent board member shall serve out the board member's term of office and succeeding board members shall be nominated and elected in accordance with Section 5030. If two or more trustee areas are established at an election that are not represented in the membership of the governing board of the school district or community college district, the county committee shall determine by lot the trustee area from which the nomination and election for the next vacancy on the governing board shall be made.

(b) If a proposal for rearrangement of boundaries is approved by a majority of the voters voting on the measure, or by the county committee when no election is required, or by the board, and if the boundary changes affect the board membership, any affected incumbent board member shall serve out the board member's term of office and that member shall continue to represent the constituents residing in the area boundaries from which the member was elected for the duration of that term of office. Succeeding board members shall be nominated and elected in accordance with Section 5030.This section does not prevent a board from assigning a trustee or school district or community college district official to provide constituent services to residents of an area that is temporarily not represented by a trustee due to redistricting.

(c) If a proposal for abolishing trustee areas is approved by a majority of the voters voting at the election, the incumbent board members shall serve out their terms of office and succeeding board members shall be nominated and elected at large from the district.