35 ILCS 110/3c
For purposes of this Act, a corporation, limited liability company, society, association, foundation or institution organized and operated exclusively for educational purposes shall include: all tax-supported public schools; private schools which offer systematic instruction in useful branches of learning by methods common to public schools and which compare favorably in their scope and intensity with the course of study presented in tax-supported schools; vocational or technical schools or institutes organized and operated exclusively to provide a course of study of not less than 6 weeks duration and designed to prepare individuals to follow a trade or to pursue a manual, technical, mechanical, industrial, business or commercial occupation.
However, a corporation, limited liability company, society, association, foundation or institution organized and operated for the purpose of offering professional, trade or business seminars of short duration, self-improvement or personality development courses, courses which are avocational or recreational in nature, courses pursued entirely by open circuit television or radio, correspondence courses, or courses which do not provide specialized training with a specific vocational or technical field shall not be considered to be organized and operated exclusively for educational purposes.
35 ILCS 110/3c