SHOREWOOD, Wis. (AP) — A Wisconsin middle school gym teacher has been placed on indefinite leave while district officials look into claims that she separated students in one class by race and assigned the black children to research games that enslaved children played.

The Shorewood Intermediate School teacher was instructing seventh-graders about games from around the world on April 1 when she allegedly gave the assignment to the black students, Shorewood School District Superintendent Bryan Davis said in a Thursday letter to parents. He didn’t name the teacher.

“We take these allegations extremely serious,” Davis wrote. “Throughout this situation, student safety and well-being have been our top priority.”

One of the black students, MaHailey Stephens, told WITI-TV that she and her classmates were separated into groups based on race and asked to research games from their cultures.

“I went to my mom, I’m like, ‘mom, what are slave games?'” she said.

Her mother, Reshunda Stephens, told the station that the same teacher asked her older daughter to be part of “the colored club,” last year.