Upon the establishment of a new school district of the first class as provided for in *RCW
28A.315.580 containing no former first-class district, the directors of the old school districts who reside within the limits of the new district shall meet at the call of the educational service district superintendent and shall constitute the board of directors of the new district. If fewer than five such directors reside in such new district, they shall become directors of said district and the educational service district board shall appoint the number of additional directors to constitute a board of five directors for the district. Vacancies, once such a board has been reconstituted, shall not be filled unless the number of remaining board members is less than five, and such vacancies shall be filled in the manner otherwise provided by law.
Each board of directors so constituted shall proceed at once to organize in the manner prescribed by law and thereafter shall have all the powers and authority conferred by law upon boards of directors of first-class school districts until the next regular school election in the district at which election their successors shall be elected and qualified. At such election no more than five directors shall be elected either at large or by director districts, as the case may be, two for a term of two years and three for a term of four years: PROVIDED, That if such first-class district is in a county with a population of two hundred ten thousand or more and contains a city of the first class, two directors shall be elected for a term of three years and three directors shall be elected for a term of six years.