105 ILCS 5/14C-3
Each school district shall ascertain, not later than the first day of March, under regulations prescribed by the State Board, the number of English learners within the school district, and shall classify them according to the language of which they possess a primary speaking ability, and their grade level, age or achievement level.
When, at the beginning of any school year, there is within an attendance center of a school district, not including children who are enrolled in existing private school systems, 20 or more English learners in any such language classification, the school district shall establish, for each classification, a program in transitional bilingual education for the children therein. A school district may establish a program in transitional bilingual education with respect to any classification with less than 20 children therein, but should a school district decide not to establish such a program, the school district shall provide a locally determined transitional program of instruction which, based upon an individual student language assessment, provides content area instruction in a language other than English to the extent necessary to ensure that each student can benefit from educational instruction and achieve an early and effective transition into the regular school curriculum.
Every school-age English learner not enrolled in existing private school systems shall be enrolled and participate in the program in transitional bilingual education established for the classification to which he belongs by the school district in which he resides for a period of 3 years or until such time as he achieves a level of English language skills which will enable him to perform successfully in classes in which instruction is given only in English, whichever shall first occur.
An English learner enrolled in a program in transitional bilingual education may, in the discretion of the school district and subject to the approval of the child's parent or legal guardian, continue in that program for a period longer than 3 years.
An examination in the oral language (listening and speaking), reading, and writing of English, as prescribed by the State Board, shall be administered annually to all English learners enrolled and participating in a program in transitional bilingual education. No school district shall transfer an English learner out of a program in transitional bilingual education prior to his third year of enrollment therein unless the parents of the child approve the transfer in writing, and unless the child has received a score on said examination which, in the determination of the State Board, reflects a level of English language skills appropriate to his or her grade level.
If later evidence suggests that a child so transferred is still disabled by an inadequate command of English, he may be re-enrolled in the program for a length of time equal to that which remained at the time he was transferred.
105 ILCS 5/14C-3