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Students at a Chicago high school held a sit-in Wednesday in protest after a teacher allegedly told a Latino student last month to "go back to your country” when she and others declined to stand for the national anthem during an assembly.

Mary Beck, the school's principal, addressed students during the protest at Nicholas Senn High School, saying she had notified the school district soon after receiving a report of the teacher's alleged comment.

A sit-in at Senn High School in Chicago. via Twitter

"I notified everybody within three hours of receiving the report. It is all in writing," Beck said in a video posted to Twitter. "It is all time-stamped. I did my job. I continue to follow through based on the guidelines and policies that we have in place. Every time."

Students shouted back in an apparent reference to the teacher, “So why is he still here?”

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NBC News reached out to Beck for an interview Thursday but did not immediately hear back.

Yésica Salazar, 17, a senior at the high school who told NBC News she is a citizen and was born in the U.S., said the incident occurred during a Hispanic heritage assembly Jan. 30. She said she and some other students stayed seated during the national anthem to protest U.S. immigration policies, anti-immigrant rhetoric and police brutality. Two teachers told them they would need to leave if they did not stand, Salazar said.

She said one of the teachers then asked another senior if she was eligible for free or reduced lunch. After that student said "yes," the teacher said she should stand because people had died for this country. After that student left the auditorium, Salazar said the teacher asked her if her legs were broken. She said "no," and began to explain why she was sitting, Salazar said.

"Before I could finish my sentence, he responds back with the famous line: 'Go back to your country.'" she said.

Chicago Public Schools told NBC News in a statement that it is "committed to fostering learning environments that embrace and support all students, and the alleged actions of the teacher in question run counter to our beliefs and priorities as a school district."

The district's press secretary, James Gherardi, said it has opened an investigation into the teacher's alleged remark. He said the district supports students' raising concerns peacefully.

But Chicago police said a 15-year-old girl was arrested at the sit-in Wednesday and charged with battery after officers broke up a fight between two female students. The girl allegedly pushed a 55-year-old man, causing him to fall, police said.

Senn High School is predominantly Latino and black. According to data from the 2018-19 school year, 25.8 percent of the student body is black, 42.3 percent Latino, 11.2 percent white and 17.5 percent Asian.

Salazar said that after the teacher told her to "go back to your country," she told him she was a citizen. An argument ensued, according to Salazar, and she was later told to leave the auditorium.

Salazar said she felt offended by the teacher's comment because her parents came from Mexico for a better life, and, "I have family who have faced discrimination."

The school district declined to comment Thursday on whether the teacher was still in the classroom.