105 ILCS 5/24-13
The contractual continued service status of a teacher is not affected by his attained age, promotion, absence caused by temporary illness or temporary incapacity as defined by regulations of the employing board, leave of absence mutually agreed upon between the teacher and the board, or because of absence while in the military service of the United States. If a teacher is elected to serve in the General Assembly, the board shall grant him a leave of absence if he so requests. A teacher employed to replace one in the military service of the United States or one serving in the General Assembly does not acquire contractual continued service under this Article. If a teacher is elected to serve as an officer of a state or national teacher organization that represents teachers in collective bargaining negotiations, the board shall grant the teacher, upon written request, a leave (or leaves) of absence of up to 6 years or the period of time the teacher serves as an officer, whichever is longer.
105 ILCS 5/24-13