A Minnesota teacher has been placed on leave after a video showing her using a racial slur while speaking to middle school students went viral, the district said Thursday.

Saint Paul Public Schools Superintendent Joe Gothard promised in a statement to take aggressive action after video was posted online of teacher Wendy Brilowski using the N-word at Highland Park Middle School.

Brilowski can be heard saying " f------ n------" in the video, which the district verified was authentic to NBC News. Another staff member said "she's repeating what you're saying" after the slur was used, but the roughly 20-second video does not show any students speaking prior to Brilowski's comments.

The district did not provide more detail on the context of what happened before or after the video was taken, but did confirm the incident occurred during school hours. Brilowski did not immediately respond to a request for comment from NBC News.

Gothard also apologized in a video to parents, adding that foul and racist language has no place in the district.

"As educators, we have to be held to a higher standard and we know that this situation represents a failure on our part," Gothard said. "And we will not fall silent in the face of racism in our schools."

Brandy Coleman, the mother of one of the students, told NBC-affiliate KARE that the video was the boiling point of tensions between Brilowski and her daughter that had been simmering over the course of many months. Her daughter said that Brilowski previously called her and other students "negroes," the mother told KARE.

“It breaks my heart that I didn’t know the magnitude of the situation so that I could intervene before that video,” she said.