Summer, 13, suffered a black eye, a welt on the side of her face and cuts to her eyelid in the attack, which occurred as she was waiting to catch the bus home.
A resident who saw the incident took Summer into his house to keep her safe. Anderson arrived 10 minutes later to find her daughter bleeding and distressed.
"I saw her with blood coming out of her eye from the cuts. She just saw me and cried and my heart stopped,'' she said.
Police allege she chased and assaulted the alleged ringleader. She said yesterday she had experienced "a mother's rage'' after seeing her daughter hurt.
Two 14-year-old girls were arrested after the attack.
Anderson says her daughter is too terrified to return to Kaipara College and she may send her to another school next year.
Summer said the group attacked her because they believed she was going to fight the cousin of one of the girls - a rumour she said was untrue.
Kaipara College principal John Grant said although he was "always disappointed when students end up fighting'' it was difficult to prevent such incidents, which he described as rare.
"These things happen. They happen in the adult world and in the adolescent world,'' he said.
Board of trustees' chairman Stanley Phillips agreed.
"Kids are kids. Things get blown out of proportion by kids _ we have to let the police and the principal of the school do the investigation but we are aware as a board of society's concerns of violence and Facebook and text (bullying),'' he said.
The school is investigating with police and the offenders were likely to be stood down or suspended, Mr Grant said.
An anti-bullying programme in place at the school had "strong student support'', he said.
