Charles Ventura | USA TODAY

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Mark Humphrey, AP

A charter school in Texas has apologized after eighth-grade students were asked to list the "positive" and "negative" aspects of slavery for an American history class.

"To be clear, there is no debate about slavery. It is immoral and a crime against humanity," Aaron Kindel, superintendent of Great Hearts Texas, said in a Facebook statement Thursday. "We sincerely apologize for the insensitive nature of this offense."

Earlier in the week, Roberto Livar posted a picture of the assigned worksheet, titled "The Life of Slaves: A Balanced View," that his son, Manu, said was asked to complete at Great Hearts Monte Vista North campus in San Antonio, according to HuffPost.

The issue was later brought to the public's attention when Rep. Joaquin Castro, D-Texas, sent out a tweet Thursday, slamming the assignment as "absolutely unacceptable."

"Asking students to complete such an assignment challenges the reality that slavery was utterly dehumanizing," Castro said in a statement, according to KENS-TV. "It is also an affront to the basic idea of human liberty. Great Hearts Charter network should do a full review of its history curriculum and those who teach it."

Kindel, who said the incident was limited to one teacher, added that the school's headmaster and teachers will "spend time with the impacted students to explain the mistake." Kindel also said that Great Hearts is conducting an audit of the textbook, Prentice Hall Classics: A History of the United States, to see if it should be permanently replaced.

Pearson, the textbook's publishing company, distanced itself from the controversy.