An 18-year-old was stabbed in a fight at Otahuhu College on Wednesday night.
Police were called to reports of the stabbing at around 10pm. The victim was stabbed in the abdomen and received serious injuries.
The school was holding practices for a Polyfest competition, according to the Otahuhu College website.
The alleged offender is described as a male in his late teens, around 178cm tall with a skinny build and afro.
He was wearing a black t-shirt, cream shorts, black sneakers and a cap.
Anyone who witnessed the incident or knows the identity of the offender is asked to contact the Counties Manukau Crime Squad on (09) 261 1321.