If the United States Congress enacts legislation, when the state legislature is not in session, making money available to the states for teachers' salaries, the governor or the board as the federal law may require may accept and use part or all of the federal money made available to the state to increase teachers' salaries according to a minimum salary schedule to be arrived at by the board. The governor or the board as federal law may require may use money appropriated by the legislature for teachers' salaries for matching purposes and may expend federal money so obtained for increased teachers' salaries in addition to state money already appropriated for that purpose. Any modified state minimum salary schedule arrived at as a result of receiving federal money may be put into effect by executive order signed by the governor or by order of the board, whichever appears to be the most nearly proper under federal law. This minimum salary schedule shall remain valid under the order until it is altered or approved in full by the legislature.