A Superintendent of Schools for each county may be elected by the qualified electors thereof at each gubernatorial election or may be appointed by the county board of education, and the manner of the selection shall be determined by a majority vote of the electors of the county voting on the question; provided, that two or more counties may, by an election conducted pursuant to Section 3.2 of this article, unite for the purpose of electing or appointing one joint superintendent for the counties so uniting.