105 ILCS 5/3-14.2
Except in regions established within that portion of a Class II county school unit outside of a city of 500,000 or more inhabitants, the county superintendent of schools shall exercise supervision and control over all school districts within the county. If a district is divided by a county line or lines the county superintendent in the county where the majority of the children attend school at the time the district is organized shall exercise supervision and control over all aspects of supervision, reports, and financial accounting of the district until it has been determined by the State Superintendent of Education that 60 per cent of the children attend school in another county or that a majority of the children have attended a school in another county for three consecutive years and the school board has adopted a resolution requesting the supervision and control be transferred to the county superintendent in the county in which the majority of children attend school. The county superintendent under whose direction a school district has been established shall retain supervision and control until July 1 following the date of the election establishing the district. Whenever a change in supervision and control shall result from a change in school district boundaries, population shifts, or other cause, such change in supervision and control shall not be effective until July 1 following the date of its determination. All references to the county superintendent of schools, in relation to school districts, in this Act shall be interpreted to mean the county superintendent of schools having supervision and control of the district or districts as defined in this Section.
105 ILCS 5/3-14.2