When a county board of education desires to provide for the joint maintenance of a public school by a county in this state and an adjoining county in another state, said board shall ascertain what agreement with the authority having power to bind the county in the other state may be secured for such joint maintenance, and if the county board deems the conditions of the agreement mutually advantageous, it shall certify the same, together with all the facts, to the State Superintendent of Education. The State Superintendent of Education shall investigate and, if he deems the proposed arrangement advantageous, shall approve the same. Such approval shall authorize the joint maintenance of such state-line schools.