105 ILCS 5/24-6.1
Every school board may grant a sabbatical leave of absence to a teacher, principal or superintendent performing contractual continued service, for a period of at least 4 school months but not in excess of one school term, for resident study, research, travel or other purposes designed to improve the school system. The grant of a sabbatical leave by a school board shall constitute a finding that the leave is deemed to benefit the school system by improving the quality and level of experience of the teaching force.
This leave may be granted after completion of at least 6 years of satisfactory service as a full time teacher, principal or superintendent and may again be granted after completion of a subsequent period of 6 years of such service. However, 2 sabbatical leaves, each consisting of at least 4 months but totaling no more than the equivalent of one school year, may be granted within a 6 year period. A leave granted for a period of one school year or less shall bar a further sabbatical leave until completion of 6 years additional satisfactory service, except that 2 leaves which total no more than the equivalent of one school year shall bar a further sabbatical leave only until the completion of 6 years additional satisfactory service following the completion of the first such leave. The leave shall be conditional upon a plan for resident study, research, travel or other activities proposed by the applicant and deemed by the board to benefit the school system, which plan shall be approved by the board and not thereafter modified without the approval of the board.
Before a leave is granted pursuant to this Section, the applicant shall agree in writing that if at the expiration of such leave he does not return to and perform contractual continued service in the district for at least one school year after his return, all sums of money received from the board during his sabbatical leave will be refunded to the board unless such return and performance is prevented by illness or incapacity.
During absence pursuant to such leave, such teacher, principal or superintendent shall receive the same basic salary as if in actual service, except that there may be deducted therefrom an amount equivalent to the amount payable for substitute service. However, such salary after deduction for substitute service shall in no case be less than the minimum provided by Section 24--8 of this Act or 1/2 of the basic salary, whichever is greater. The person on leave shall not engage in any activity for which salary or compensation is paid unless the activity is directly related to the purpose for which the leave is granted and is approved by the board. A sabbatical leave may be granted to enable the applicant, if otherwise eligible, to accept scholarships for study or research. Unless justified by illness or incapacity, failure of any person granted a leave under this Section to devote the entire period to the purposes for which the leave was granted shall constitute a cause for removal from teaching service.
Upon expiration of a leave granted pursuant to this Section, and upon presentation of evidence satisfactory to the board showing compliance with the conditions of the leave, the teacher, principal or superintendent shall be returned to a position equivalent to that formerly occupied. The contractual continued service status of the person on sabbatical leave shall not be affected.
Absence during a leave granted pursuant to this Section shall not be construed as a discontinuance of service for any purpose, including progression on the salary schedule if one is in effect in the district. The board shall pay the contribution to the Teachers' Retirement System required of the person on leave computed on the annual full-time salary rate under which the member last received earnings immediately prior to the leave or a proportionate part of such rate for a partial year of sabbatical leave credit.
This Section in no way limits the power of the board to grant leaves for other purposes.
105 ILCS 5/24-6.1