The school boards of any school district of the first class having within its boundaries a city with a population of four hundred thousand people or more shall establish the director district boundaries. Appointment of a board member to fill any vacancy existing for a new director district prior to the next regular school election shall be by the school board. Prior to the next regular election in the school district and the filing of declarations of candidacy therefor, the incumbent school board shall designate said director districts by number. Directors appointed to fill vacancies as above provided shall be subject to election, one for a six-year term, and one for a two-year term and thereafter the term of their respective successors shall be for four years. The term of office of incumbent members of the board of such district shall not be affected by RCW
28A.343.300,
28A.343.600,
28A.343.610,
28A.343.660, and
28A.343.670.