WASHINGTON (AP) — The principal of a Washington, D.C., elementary school says a lesson about the Civil War and Reconstruction era went wrong when some fifth graders asked their black classmates to portray slaves.

Lafayette Elementary School principal Carrie Broquard detailed the mistake in a letter to parents that explained the learning exercise won’t be offered in the future, The Washington Post reported Monday. Part of the lesson involved students creating a dramatic reading or podcast.

“Unfortunately, several students of color were asked by their peers to portray inappropriate and harmful roles,” Broquard wrote.

The roles, which were requested by students after they broke into groups, included that of an enslaved person and a person of color drinking from a segregated water fountain, according to letters from the school. Broquard said the students reported being uncomfortable with such casting and others were uncertain of how to respond or intervene. School staff will undergo diversity training next month, she said.

Broquard didn’t respond to the newspaper’s request for comment.