The principal of a Washington, DC, elementary school has apologized after black fifth-graders were asked to portray slaves during an in-class assignment, according to reports.

Principal Carrie Broquard sent a letter home to parents at Lafayette Elementary School saying that the lesson won’t be given to future classes after “several students of color” were asked to play troubling roles, the Washington Post reports.

The assignment took place after weeks of instruction about the Civil War and the Reconstruction era, and students were asked to create a dramatic reading or a podcast to demonstrate what they had learned, Broquard said.

“We learned that during group work, a few students of color had been asked by their peers to pay roles that are inappropriate and harmful – a person of color drinking from a segregated water fountain and an enslaved person,” the letter read.

The students “expressed discomfort” after being asked to play the roles. Staffers at the school will now undergo diversity training next month, Broquard said.

A spokesperson for DC public schools referred to Broquard’s letter when asked for additional details about the assignment, the Washington Post reports.

It’s unclear exactly when the assignment, which Broquard characterized as a “mistake,” was given to the students. A copy of the letter obtained by NBC News said it occurred during a recent fifth-grade class.

“As the leader of the Lafayette school community, I am distressed this happened and saddened our students were hurt,” Broquard’s letter read.