A friend of the attacker filmed the incident, which took place last Monday (Jan 30), on his cellphone.

Investigating officer Lucky Biyela said careful procedures were being followed by police because a minor was being investigated for a serious crime.

"It is a matter that will go to court," he said.

Krugersdorp High School principal Ivan Bailey confirmed there had been an external governing body disciplinary hearing to investigate the attack on Tuesday night. The girl had been allowed to return to school.

"A principal cannot expel a learner. There is a disciplinary procedure that has to be followed, and this has been done."

Bailey said the attack was the culmination of a series of "shocking conversations" on Facebook and Blackberry's messenger service.

"We do have school counsellors involved," he said. "Cyberbullying is something we take very seriously."

Vanessa Wienand, the mother of the Grade 10 girl who was attacked, said she was at her wits end on how to stop the bullying which involved several girls.

"This has gone on for months. My child has a right to safe education and this right is being violated."

Wienand laid the charge on behalf of her daughter against the girl who hit her with the juice bottle.

"There has been a little gang of them calling her fat, insulting her and being generally nasty," said the mother.

"I have now handed all of the messages they have been sending her to the police."

Wienand said she was angry because the school did not warn her that the attacker would be back at school on Wednesday. She was unable to prepare her daughter.

In the video, the attacker walks purposefully across the playground. When she sees her victim, she and her friends surround her. The attacker then raises her arm and brings a full bottle of juice down on the taller girl's head.

The teenager steps back looking dazed and shocked. No teachers are visible.

Gauteng education department spokesman Charles Phahlane said he was aware of the matter and asked that the video be forwarded to him. He said he would comment on what had happened once he had spoken to the school.