A charter school in Texas apologized on Friday after students were asked to write a list of the positive aspects of slavery. 

In a Facebook post, Aaron Kindel, the superintendent of the Great Hearts academies in Texas, apologized for the eighth-grade history class assignment, saying that the incident was limited to just one teacher at one particular school.

“In the 8th grade American History class students were asked to reflect on the differing sides of slavery,” the Facebook post reads. “To be clear, there is no debate about slavery. It is immoral and a crime against humanity.”

Kindel said that Great Hearts academies was taking the incident seriously, and had placed the teacher responsible for the assignment on leave.

At the same time, the charter school system said that it had removed the textbook, “Prentice Hall Classics: A History of the United States,” from its classrooms, and was conducting audit of the material.

“If we deem this textbook imprudent, we will permanently remove it and replace it with a history book that accurately reflects our values,” Kindel wrote.

A private elementary school in Wisconsin came under fire in January after fourth graders were asked to do an assignment listing both the “good” and “bad” reasons for slavery. 

That school, Our Redeemer Lutheran School in Wauwatosa, issued an apology, writing in a letter to parents that the homework assignment was racially offensive and “showed a lack of sensitivity.”