105 ILCS 5/10-22.4

To dismiss a teacher for incompetency, cruelty, negligence, immorality or other sufficient cause, to dismiss any teacher on the basis of performance and to dismiss any teacher whenever, in its opinion, he is not qualified to teach, or whenever, in its opinion, the interests of the schools require it, subject, however, to the provisions of Sections 24-10 to 24-16.5, inclusive. Temporary mental or physical incapacity to perform teaching duties, as found by a medical examination, is not a cause for dismissal. Marriage is not a cause of removal.