720 ILCS 5/21.2-5
For the purposes of this Article the words and phrases described in this Section have the meanings designated in this Section, except when a particular context clearly requires a different meaning.
"Public institution of education" means an educational organization located in this State which provides an organized elementary, secondary, or post-high school educational program, and which is supported in whole or in part by appropriations of the General Assembly , a unit of local government or school district .
A person has received "due notice" if he, or the group of which he is a part, has been given oral or written notice from an authorized representative of the public institution of education in a manner reasonably designated to inform him, or the group of which he is a part, that he or they should cease such action or depart from such premises. The notice may also be given by a printed or written notice forbidding entry conspicuously posted or exhibited at the main entrance of the building or other facility, or the forbidden part thereof.
"Force or violence" includes, but is not limited to, use of one's person, individually or in concert with others, to impede access to or movement within or otherwise to interfere with the conduct of the authorized activities of the public institution of education, its trustees, school board members, superintendent, principal, employees, students or invitees.
720 ILCS 5/21.2-5