Police have criticised the parents who knew about a planned fight that resulted in a cowering 15-year-old girl being bashed around the head.

Video footage of the incident, outside a Waikato college, appears to show the victim being pushed to the ground, punched and kicked in the head by a woman while the girl cowers on the pavement.

Sergeant Daniel Peat told Fairfax police were disappointed action wasn't taken to prevent the fight from eventuating.

"We are disappointed that adults and parents knew about this organised fight and did nothing about it.

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"We are dealing with lots of people at present and it should be all tied up over the weekend," he said.

A teenage schoolgirl was allegedly kicked in the head by a young mother outside a school this week, after Facebook threats escalated.

The victim's mother, who has not been named to protect the identity of her daughter, said she "feels sick" over the alleged assault which caused her daughter to bleed from her ear and potentially need antibiotics to treat infected grazes on her face, arms and legs.

She said she reported the incident to police, but was unhappy with the speed of their response.

"I feel like I am banging my head against a brick wall. There should be an arrest by now, [my daughter] is in quite a bad way."

A police spokeswoman said officers were notified on Monday of the incident.

"Inquiries are continuing as police work to determine what happened," she said.

The victim's mother said the incident stemmed from a Facebook fight between her daughter's friends, and another teenage girl from a nearby town.

The teens arranged to meet at 2.30pm outside the school, but when one of the groups showed up, they were allegedly met by a teenage girl and a group of her adult relatives, including a woman said to be a 20-year-old mother.

The victim's mother said there was a fight between one of her daughter's friends and the other teen.

Afterwards, she said the 20-year-old attacked her daughter, and that was the incident caught on film.

"My daughter and her friends didn't know they were going to get there and there was going to be grown adults, it makes me sick.

"I send my daughter to be safe at school . . . but now there is a video of her being booted in the head across from the school gates."

The college the fight happened outside is yet to respond to Herald requests for comment.

The incident follows a mass brawl between over 100 students at an Auckland KFC last week.