SAN ANTONIO -- 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 teacher at Great Hearts Monte Vista who distributed a worksheet titled "The Life of Slaves: A Balanced View" has been placed on leave.

Aaron Kindel, the superintendent of Great Hearts Texas, said in a statement the school would audit the textbook associated with the lesson.

"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, CBS affiliate KENS-TV reports.

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"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. Rep. Joaquin Castro, D-Texas, drew attention to the issue on Thursday when the Democrat tweeted that the worksheet was "absolutely unacceptable."

This is absolutely unacceptable. A @GreatHeartsTX charter school in San Antonio asked students to complete a “balanced view” assignment about slavery, requiring them to list the “positive aspects” of slave life. The teacher worked from a @pearson textbook. pic.twitter.com/mzEWty68tB — Joaquin Castro (@JoaquinCastrotx) April 19, 2018

"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.