105 ILCS 5/12-20
If a recognized two or three year high school is conducted in a non-high school district, any eighth grade graduate residing in the district, upon the approval of the county superintendent of schools, may attend a recognized high school more convenient in some district other than the district in which he resides and his tuition shall be paid by the board of education of the non-high school district. If no recognized two or three year high school is conducted in a non-high school district, any eighth grade graduate residing in the district may attend any recognized two, three or four year high school, and his tuition shall be paid by the board of education of the non-high school district.
When non-high school territory is eliminated from the non-high school district the pupils residing in the former non-high school territory who have been attending a recognized public high school in another district as tuition pupils may continue to attend such school until their high school education is finished and the annexing board shall pay the tuition after the annexation of the former non-high school territory.
"Eighth grade graduate" in this section means any person of school age who gives satisfactory evidence of having completed the first eight grades of school work by presenting a certificate of promotion issued by the school board of the school attended by him, or by passing an examination given by the county superintendent of schools or by passing an examination given by the school attended.
"Recognized high school" in this section means any public high school providing a course of two or more years of work approved by the Superintendent of Public Instruction.
105 ILCS 5/12-20