A New York private school has agreed to take steps to improve campus diversity—including hiring a “chief diversity officer”—after a state investigation found that a fifth-grade teacher held mock “slave auctions” in which white students bid on their black peers.

In a release Wednesday, New York Attorney General Letitia James revealed The Chapel School—a private Lutheran school in Bronxville that charges $12,770 in tuition for elementary schoolers—was ordered to “make significant changes to its approach to diversity and inclusion,” saying the mock auctions “had a profoundly negative effect on all of the students present.”

James said the former teacher, who has since been fired by the school, ran two mock auctions in two fifth-grade classes in early March “as part of a curriculum on colonial America.”

During the “auctions,” the teacher had black students stand outside in the school’s hallway, where she placed “imaginary chains” on them, the attorney general said. The teacher then instructed the black students to line up against the wall inside her classroom and “proceeded to conduct a simulated auction of the African-American students in front of the rest of the class,” the release states.

According to NBC News, a mother of a student said the white teacher allowed white students to bid or “buy” the black students.

The AG’s office also found the school had accumulated complaints from parents about Chapel School’s “lack of racial sensitivity” before the mock trials took place—including concerns about “unequal discipline of students on the basis of race, a lack of racial sensitivity and awareness in school curricula, and a lack of diversity among the teaching faculty.”

“Every young person—regardless of race—deserves the chance to attend school free of harassment, bias, and discrimination,” James said in the release. “Lessons designed to separate children on the basis of race have no place in New York classrooms, or in classrooms throughout this country.”

As part of its agreement with the AG’S office, the school will also be required to hire a “chief diversity officer,” create a new Code of Conduct with James’ approval, and retain a diversity consultant.

“The Chapel School reached a timely resolution with the Attorney General to ensure that our focus remains on the well-being of our community as we move forward in continued reflection, action, and growth,” the school said.

The AG’s office and The Chapel School did not return requests for comment.