105 ILCS 5/3A-9
An educational service region, consisting of 2 or more counties, may be restructured by the disconnection of a county from the educational service region as provided in this Article. However, no educational service region involved in the disconnection may contain less than 33,000 inhabitants after the disconnection, unless it is a region which after the disconnection contains an area that was formed from the consolidation of 3 or more regions.
Disconnection may be initiated by a petition requesting an election on whether the county should be disconnected from the present educational service region and whether the county should be consolidated with a different specified educational service region. A petition shall be signed by 10% of the legal resident voters of the county to which the petition refers; the petitioners' addresses shall be included.
A petition shall be filed with the regional superintendent of the educational service region of which the county is a part not more than 99 nor less than 92 days prior to a regular scheduled election. The regional superintendent and the county clerk shall determine the sufficiency of the petition. If the petition is deemed sufficient by the regional superintendent and the county clerk, the regional superintendent shall call an election at the next regular scheduled election for the purpose of presenting a public measure, in accord with the petition, to the voters of the county to be disconnected as specified in the petition.
105 ILCS 5/3A-9