A middle school teacher at Hempstead's Alverta B. Gray Schultz Middle School was in a classroom Wednesday afternoon when a parent went past a security checkpoint and waited outside her door to confront her, police and union officials said.

The parent, later identified as Annika McKenzie, 34, insisted in engaging the teacher for reasons that haven't been disclosed. The teacher was heard asking the woman to get a security pass and then calling for security before things got worse, police said.

"The parent continued the conversation, got into an argument and then pushed the teacher against the wall, put her in a headlock and threw her to the hallway floor," Hempstead Village police Chief Michael McGowan said.

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A crowd gathered, McGowan said, "and a juvenile female relative of the adult began to punch the teacher in the head."

The attack -- recorded on the school's video surveillance system -- rendered the teacher unconscious for several minutes, according to Elias Mestizo, president of the Hempstead Classroom Teachers Association. Police said they received the 911 call about 2 p.m. and arrested McKenzie and a 14-year-old student who they believe is the woman's niece.

Both were charged with second-degree assault on school grounds, a felony. McKenzie also was charged with second-degree strangulation. The girl was not identified because she is a minor, but she was to appear in Family Court. The teachers' union chief said another child may have been involved, but police did not confirm those details.

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McKenzie, a Hempstead Village resident who had a 2001 grand larceny arrest that was pleaded down to petty larceny, appeared without an attorney Thursday in First District Court in Hempstead, court records show. Bail was set at $5,000 cash or $7,500 bond. She is due back in court Tuesday. It was unclear Thursday night whether she posted bail. Attempts to reach McKenzie were unsuccessful.

McGowan said his department "put some added patrols outside the school for dismissal" Thursday. The district administration did not respond to specific inquiries about corrective measures or any other steps in response to the attack.

Annika McKenzie, 34, has been charged with second-degree assault on school grounds, a felony, and second-degree strangulation in connection with an assault on a teacher at Hempstead's Alverta B. Gray Schultz Middle School, which police said took place on April 15, 2015. Photo Credit: NCPD

District Superintendent Susan Johnson said at Wednesday's school board meeting that the district had reviewed video to assist in the investigation.

A statement from school board President Lamont Johnson, no relation to the superintendent, said the district "will do everything we can to ensure our students are safe in our schools."

Union chief Mestizo, who called for a wider investigation and a public report of incidents, said the teaching staff was horrified with what he termed a failure of leadership.

He told the board at its meeting that a couple of teachers had been threatened with rape or death in other incidents and had not seen much of a response to complaints.

The victim's name was not released. Mestizo said she teaches math and is a dedicated instructor with more than 20 years in Hempstead. He said she's home, "in a lot of pain" and emotionally rattled.

"Those who know her have expressed that not only is she passionate with what she does, but that students really care for her," Mestizo said.

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The case had been referred to Nassau County Police Department's Third Squad.