105 ILCS 5/24-21
The directors shall pay the wages of teachers in a manner agreed upon by the board, but at least 1 payment shall be made during each school month. The directors shall issue and deliver to the teacher an order on the school treasurer for the amount of salary due. The order shall state the rate and time for which the teacher is paid. It is unlawful for the directors: (1) to issue an order before they have certified to any schedule then required to be made; (2) after the date for filing schedules as fixed by law, to certify any schedule not delivered to them before that date when such schedule is for time taught before the first of July preceding; (3) to give an order in payment of a teacher's wages for the time covered by such delinquent schedule. Teachers not covered by a negotiated collective bargaining agreement may elect to receive payment of wages over either a 10 or 12 month period annually.
105 ILCS 5/24-21