There shall be a county board of education in each county which, except as otherwise expressly provided, shall be composed of seven members, six of whom shall be appointed by the Governor upon the recommendation of the Senator and at least one half of the members of the House of Representatives from the county, who shall serve terms of four years each commencing on May first in each year preceding the year of a presidential election. Any vacancies on the county boards of education shall be filled in the same manner for the unexpired terms. The county superintendents of education shall be ex officio members of the county boards of education in those counties in which the county superintendent of education is elected by the people and in counties in which the county superintendent of education is not elected by the people the seventh member shall be appointed in the same manner and for the same term as the other six members. No employee of a public school system other than the county superintendent of education shall be eligible to serve as a member of a county board of education.