(1) In each county with a population of two hundred ten thousand or more, first-class school districts containing a city of the first-class shall hold their elections biennially as provided in RCW
29A.04.330.
(2) Except as provided in RCW
28A.343.610, the directors to be elected may be elected for terms of six years and until their successors are elected, qualified, and assume office in accordance with *RCW
29A.20.040.
(3) If the board of directors of a school district pursuant to subsection (1) of this section reduces the length of the term of office for school directors in the district from six to four years, the reduction in the length of term must not affect the term of office of any incumbent director without his or her consent, and a provision must be made to appropriately stagger future elections of school directors.