People should be able to attend school sports events without putting up with violence, police say.

They are investigating an all-in brawl at a rugby game between Otahuhu College and Tangaroa College in Auckland yesterday, which left a 14-year-old boy knocked out cold.

Witnesses said it was a 'disgusting' scene, that turned into complete chaos, with spectators getting involved.

"It was havoc...like a scene from Game of Thrones. It was wrong for the game as well, it killed the game," Vaelua Noutata said, while spectator Sei Alele Vaihu claimed "it was really bizzare."

"Suddenly all you could see was students fighting and parents getting involved as well, hitting students with umbrellas."

Senior Sergeant Jeremy Field insisted that this sort of behaviour is not tolerated.

"We want everyone who attends sporting occasions like this to be safe and feel safe while attending," he said.

While the injured teenager was taken to hospital in a serious condition, his condition quickly improved and he was able to speak to police.

Senior Sergeant Field claims officers are following strong lines of inquiry about the person responsible for the boy's injuries.