A black school security guard has been fired after asking a pupil not to call him the N-word.
Marlon Anderson said the teenager, who is also African American, used the racial slur repeatedly to refer to him.
He responded to a call about the student, who was being disruptive, on 9 October at Madison West High School, Wisconsin.
The 48-year-old said the teenager called him multiple obscenities, including the N-word.
Mr Anderson told the pupil not to use the slur. He repeated the word during the exchange and was subsequently fired.
“Short story.... I get called a b**** ass n***** by a student, I responded do ‘not call me a n----!’ And I got fired,” the security guard wrote on Facebook.
Madison schools have a zero tolerance policy on staff using racial slurs.
At least seven Madison School District employees resigned or were dismissed over using such language in front of students in the last school year.
Mr Anderson was fired on Wednesday after 11 years working for the Madison Metropolitan School District.
He said he was just trying to defend himself and argued that the context of the exchange should be taken into account.
“My understanding of the policy was white staff shouldn’t use the N-word under any circumstances,” the security guard told NBC News.
“But I had no idea me being called the word and me telling the student not to call me the word would get me fired.”
Hundreds of pupils at Madison West walked out of classes on Friday to protest Mr Anderson’s dismissal.
Around 1,500 pupils marched through Madison to the school district offices, chanting ”Hey-hey, hey-ho, zero tolerance has got to go!” and “Do Better!”
The news also attracted attention on social media, with Cher, the singer, offering to pay the security guard’s legal fees if he chose to sue the board.
Karen Boran, the school’s head teacher, said the zero-tolerance approach had been applied consistently.
But Gloria Reyes, the district school board president, said she wanted the board to review its policy on racial slurs as soon as possible.
“This is an incredibly difficult situation, and we acknowledge the emotion, harm and complexity involved,” she said.
“Many people in our community and our district are grappling with that complexity, and we will continue to do so as we go forward.”
The Madison teachers’ union has filed a grievance with the school district board on Mr Anderson’s behalf. Ms Reyes said she had directed officials to handle the complaint quickly.
But Jane Belmore, the board’s superintendent, said the zero tolerance policy was designed to protect students from harm, no matter the circumstances or intent involved.
She added that “different viewpoints” had emerged and that the district would review the policy.
Mr Anderson said he was left overwhelmed by the response from pupils defending him.
“It got me a little emotional, because to be honest, you don’t get that type of response from people until you’re in a casket,” he said.
Additional reporting by agencies