An upset mother “marched” into a Hempstead school and assaulted a seventh-grade math teacher, leaving her unconscious, a Nassau County prosecutor said Tuesday.

“This defendant’s intent was to cause physical injury” to the teacher,” Assistant District Attorney Rachel Lasry told jurors in her opening statement in Mineola.

But the attorney representing Annika McKenzie said she went to the school simply to learn more after her daughter complained that a teacher had put her hands on her.

McKenzie, 35, of Hempstead, is charged with felony assault and other charges stemming from the April 15, 2015, incident at Alverta B. Gray Schultz Middle School.

The teacher, Catherine Lang-Engelhardt, is expected to testify during the trial in Nassau County Court.

Lang-Engelhardt first encountered McKenzie’s daughter and other girls carrying lacrosse sticks in a hall around 1:30 p.m. after a vice principal stopped them and asked to see their hall passes, Lasry said.

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McKenzie’s daughter cursed — first at Lang-Engelhardt, and then in response to the vice principal saying she would be suspended for profanity, according to Lasry.

The girl called her mother before the vice principal could inform her of the punishment, Lasry said.

Minutes later, the prosecutor said McKenzie was at the school waiting for Lang-Engelhardt outside her classroom around 1:45 p.m. The mother pushed her against the wall, grabbed her around her neck and slammed her to the ground, Lasry said.

Both the alleged assault and the encounter in the hall were caught on surveillance cameras, the prosecutor said.

Mineola attorney Donald T. Rollock told jurors that McKenzie’s daughter had a hall pass and was headed to orchestra class by herself when Lang-Engelhardt proceeded to “slam the child against the wall with the lacrosse stick.”

Later, as McKenzie tried to talk to Lang-Engelhardt, the teacher “bangs into her” and “goes down to the ground,” Rollock said.