Plans of any second-class district or combination of districts for the carrying out of the powers granted by RCW
28A.335.250 through
28A.335.280 shall be submitted to and approved by a board of supervisors composed of members, as follows: The superintendent of public instruction; the head of the extension department of Washington State University; the head of the extension department of the University of Washington; and the educational service district superintendent; these to choose one member from such county in which the facilities are proposed to be located, and two members, from the district or districts concerned.