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A fifth-grade teacher accused of holding a mock slave auction last week in which white students at a private school in Bronxville, New York, were urged to bid on their black classmates has been placed on indefinite leave.

The principal of the Chapel School told NBC News on Monday that a third party is conducting an independent review.

“On behalf of The Chapel School, I extend my sincerest apologies to our students, their families and the community," Michael Schultz said. "The reported racial insensitivity is unacceptable, and we do not condone any action that demeans anyone. "

Cuddy and Feder, a law firm representing the teacher, said a slave auction never took place.

"To the extent anyone took offense to a small portion of the overall lesson that day that was used solely to emphasize the tragic injustice of slavery, it certainly was never intended," a partner at the firm told NBC News. "She looks forward to continuing teaching with the same dedication, sensitivity, and passion that she has always shown."

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The allegations have prompted a response from New York Attorney General Letitia James.

“The reports of racist ‘lessons’ by a teacher at The Chapel School are deeply troubling,” James told NBC News on Monday in an emailed statement. “My office is monitoring this matter closely.”

Vernex Harding, the mother of a student at the school in Westchester County, about 15 miles north of Manhattan, told media outlets that the white teacher recently allowed white students to bid on and "buy" black students, who were to pretend to be slaves.

“I’m shocked and infuriated that this happened to my son,” Harding told the New York Daily News. “I’m very shaken.”

She said her son was "humiliated."

Harding is an educational administrator at another school, according to her LinkedIn page.

Annual tuition at The Chapel School, which enrolls students in pre-k through eighth-grade, costs up to $14,000.

The principal said all faculty and staff will be provided sensitivity training.

"Teachers will address the children impacted along with the additional support of mental health professionals," he said. "The emotional state and well-being of our students and commitment to the respect of all people are our greatest concerns.”