The election of trustees of schools shall be held in odd-numbered years at the election specified in the general election law. In townships in which no election for school trustees has been held, or in townships in which from any cause there are no trustees of schools and the law requires that there be school trustees, the election of trustees of schools shall be held at the same time.
     No person shall be nominated for the office of trustee of schools, in townships containing 20,000 inhabitants or over, except by petition signed by at least 5% or 500 of the voters of the school township in which the person is seeking nomination and election who last cast votes in the most recent election, whichever is less, filed with the township treasurer, or, in case of a first election, with the county clerk.
     A candidate for election as a school trustee, who has petitioned for nomination to fill a full term and to fill a vacant term to be voted upon at the same election, must withdraw his or her petition for nomination from either the full term or the vacant term by written declaration, which shall be signed and acknowledged by an officer authorized to take such acknowledgments and which is filed with the township treasurer in the township in which he or she is a candidate within the time provided by the general election law.