"IB" stands for "International Baccalaureate." The International Baccalaureate is a non-profit educational foundation serving students aged 3 to 19. Founded in 1968 and headquartered in Geneva, Switzerland, IB has grown immensely over the past half-century. The first IB school in the United States was established in 1971, and now there are 613 schools offering the Primary Years Programme, 720 schools offering the Middle Years Programme, 968 schools offering the Diploma Programme, and 141 schools offering the relatively new Career-Related Programme.

As of June 2021, there are 40 schools in Illinois teaching the IB Diploma Programme.

The Diploma Programme is a pre-university course of studies which is designed as a comprehensive two-year curriculum, covering the last two years of secondary education. Students can choose to earn either a certificate (by studying fewer than six IB courses) or a diploma (by completing the full program with six IB courses plus the Extended Essay and the Theory of Knowledge).

Both the IB courses and the IB examinations are given at two levels of study. Higher Level (HL) requires a minimum of 240 hours of instruction, whereas Standard Level (SL) covers a minimum of 150 instructional contact hours.

End-of-year exams are given in May or November, depending on which hemisphere the student lives in. Test scores range from a low of 1 to a high of 7. Each test score is a combination of grades earned for coursework completed in the classroom (which is evaluated by the teacher) and grades earned on final exams (which are evaluated by external examiners).

The University of Illinois at Urbana-Champaign accepts for academic credit test scores of 4, 5, 6, and 7 on all IB exams, whether Higher Level or Standard Level.