115 ILCS 5/4.10: Length of work as subject of collective bargaining.

(a) Notwithstanding any other provision of this Act or other law to the contrary, with respect to a school district organized under Article 34 of the School Code only, collective bargaining between an educational employer and an exclusive representative of its employees may include decisions to determine the length of the work and school day and the length of the work and school year.

(b) The subject or matters described in subsection (a) are permissive subjects of bargaining between the educational employer and an exclusive representative of its employees and, for the purpose of this Act, are within the sole discretion of the educational employer to decide to bargain, provided that the educational employer is required to bargain over the impact of a decision concerning the subject or matter on the bargaining unit upon request of the exclusive representative under Section 10.