SAN ANTONIO (AP) — A San Antonio charter school has apologized after a teacher asked students in an eighth grade American history class to list the positive and negative aspects of slavery.

The Great Hearts Monte Vista teacher who distributed the worksheet titled “The Life of Slaves: A Balanced View” was placed on leave and the school said it would audit the textbook associated with the lesson, said Aaron Kindel, the superintendent of Great Hearts Texas, which operates 28 public charter schools in Texas and Arizona.

“To be clear, there is no debate about slavery. It is immoral and a crime against humanity,” Kindel said in a statement posted Thursday on the Great Hearts Facebook page. He said the school’s headmaster plans to explain the mistake to the history class.

Scott Overland, a spokesman for Pearson, which published the textbook, said the company didn’t create and doesn’t endorse the worksheet assigned to the students, KENS-TV reported .

“We do not support the point of view represented in the worksheet and strongly condemn the implication that there was any positive aspect to slavery,” Overland said.

A parent of one of the students in the class posted the worksheet Wednesday on Facebook. U.S. Rep. Joaquin Castro drew attention to the issue on Thursday when the Democrat tweeted that the worksheet was “absolutely unacceptable.”

“Asking students to complete such an assignment challenges the reality that slavery was utterly dehumanizing,” Castro said in a statement. He also called on the charter school network to review its history curriculum.