An 18-year-old has been arrested following an incident at Kerikeri High on Monday which triggered the school's first full lockdown.
Senior Sergeant Peter Robinson, of Mid North police, said the youth was due in the Kaikohe District Court on Friday charged with assaulting a 14-year-old boy at the school.
Robinson said it appeared the incident started with an altercation between a 13-year-old boy, on his first day at the school, and other students.
The 13-year-old went home and returned with the 18-year-old.
Robinson alleged the 13-year-old then assaulted a 14-year-old boy, knocking him to the ground, and the 18-year-old kicked him as he lay on the ground.
At that point staff intervened and stopped the fight.
During the melee a knife was dropped on the ground.
The 14-year-old boy was not injured.
Police enquiries were continuing and a decision had yet to be made about what action, if any, to take against the 13-year-old.
Robinson said there was no gang involvement, and Monday's incident had no connection with an incident involving motorcycles at the school ball on Saturday.
Nor did the 14-year-old victim have any connection to the altercation earlier in the day on Monday.
The school went into lockdown for about 25 minutes while police looked for the offender, but the 18-year-old and 13-year-old had left in a car.
The entire 1500-student school was later evacuated onto the sports field for a roll call.
Kerikeri High School deputy principal Mike Clent said the 13-year-old was currently in a school disciplinary process.