65 ILCS 5/7-1-14
Whenever real estate owned by any school district is situated in unincorporated territory adjacent to any municipality it may be annexed thereto as follows:
The board of directors or board of education of the school district shall adopt a resolution recommending the annexation of such real estate by the municipality. The resolution shall contain a complete description of such real estate. The resolution shall direct the clerk or secretary of the school board to transmit a copy thereof to the corporate authorities of the municipality. If such corporate authorities, by a majority vote of the members then holding office, enact an ordinance providing for annexation of such real estate, it shall be considered as annexed. The ordinance shall describe the territory annexed, and a copy thereof and an accurate map of such territory shall be recorded in the office of the recorder of the county or counties wherein the annexed territory is situated.
65 ILCS 5/7-1-14