"It's the first falling out we have known amongst this lot. We've got to go back and do our work on that."
Police were also called because the incident was of a bullying nature. When asked the age of the students responsible, McMillan replied: "Fifteen-year-old male".
"Three of them are in the same year group and have probably socialised together in the past."
The school had recently been involved in anti-bullying campaigns and McMillan said the incident on Monday morning was very disappointing.
"Bullying is something we don't accept and we've done a lot of work over the recent weeks."
McMillan said one of the school nurses travelled with the teen to the hospital and when she left he had been talking and smiling.
A police spokesperson said they were notified by ambulance shortly before 11.30am that a 16-year-old male had been assaulted at the school.
The teen, who was taken to Middlemore Hospital, was in a stable condition this afternoon and awaiting further medical attention, a Counties Manukau DHB spokeswoman said.
A St John spokeswoman said two ambulances had attended the incident and one male patient had been transported to Middlemore Hospital in a critical condition.
Police have been at the scene and are making inquiries into the incident. No arrests have been made at this stage, but a police spokesperson confirmed a person was assisting police with their inquiries.
A school assembly which police attended was held on Monday afternoon to update students and to remind them of what was acceptable behaviour. McMillan was also meeting with senior students and would be holding a staff meeting tomorrow morning to discuss how they could learn from it and do things better.
"The vast majority of students are shocked and disappointed. From some very senior students, they are also disappointed that this sort of thing draws negative attention and reinforces the wrong stereotypes of what our community is really like and really about".
At the school this afternoon, some parents collecting their children said they had not heard about the news.
Lee Meen was picking up his son and was shocked to hear about the incident.
"Oh that's not good. I hope the young fella is all right."
Meen, a former student at the school, said he and his wife often spoke to their children about bullying and encouraged them to never be afraid to seek help or let them know what was happening.
Another parent, who did not want to be identified, said she understood the incident involved a year 11 student and an older student in year 12.
She said her son had let her know of the attack as soon as he got into the car.
Pupils who spoke to the Herald said they had heard a number of rumours around the school this afternoon about what had happened.
One student said he was walking to a class when he noticed several police cars arrive inside the school gates.
"There were heaps of cops, but I didn't know what was happening then."
Ministry of Education deputy secretary sector enablement and support Katrina Casey said the ministry had offered its support and guidance to the principal.
"All students deserve to feel safe at school. We take incidents of violence very seriously and most schools have clear policies and procedures in place to manage this type of unacceptable behaviour."
James Cook High School is a state co-ed secondary school in the South Auckland suburb of Manurewa and has a roll of more than 1200.
