With varsity recruiting season in full swing, high school athletes across the country are committing to play for their dream schools. But for athletes being recruited to the Ivy League the process is slightly different.

The league’s Academic Index (AI) provides a high academic barrier for athletes to meet. The metric, shrouded in privacy (the institutions are forbidden from releasing the scores), is a composite measure of students’ high school GPA, class rank, and SAT I and SAT II scores.

Each Ivy League applicant—recruited athlete or not—is given a number between 60 and 240, comprised of three different categories. The first two reflect SAT I and SAT II scores and the third is a combination of the student’s GPA and class rank. League rules dictate that any student-athlete must score at least a 176 on the AI to be offered admission, which corresponds roughly to an 1140 SAT I (on a 1600 scale) and a 3.0 GPA (on a 4.0 scale).

Students must meet different criteria, however, based on the school to which they apply. The average AI of each athletic team must remain within one standard deviation (estimated to be within 12-16 points) of the average AI score for that school’s student body.

According to The New York Times, the average AI for recruited athletes across all conferences is 150, but no Ivy League institution has an average AI below 200. Harvard’s is estimated to be around 220.

While prospective Ivy League recruits draw attention for what they do on the field, their admission is just as dependent on what they do in the classroom.