A 23-year-old man has admitted a charge laid after a brawl at Hutt Valley High School north of Wellington on Tuesday.
Kodee Samuels pleaded guilty to a charged of unlawful assembly and was remanded on bail for sentencing in Lower Hutt District Court on 26 March.
Eight others, aged between 14 and 20, have also been charged with unlawful assembly.
Given the young age of some of the accused, all eight appeared in the Youth Court.
They entered no plea and were remanded on bail to reappear in court on 25 February.
The Education Ministry has bolstered security at the school after pupils brawled with the group as they entered the grounds.
The nine were arrested after a student was set upon on Tuesday afternoon in what police have described as a melee.
A series of fights broke out after three adults and six youths not associated with the college arrived to confront a student about a previous altercation.
Police say about 30 students went to the aid of their schoolmate, and one female student received a cut to the head after a rock was thrown. More than a dozen police officers went to quell the disturbance.
Principal Ross Sinclair says the Education Ministry has arranged for security guards to patrol the school, and he is thankful that police were able to respond quickly.