A large group of intruders lay waiting in a park then attacked students at an Ōtara school, leaving one student seriously injured.

Sir Edmund Hillary Collegiate senior school principal Kiri Turketo said the group invaded the school grounds at lunchtime today.

She called police and "lots of police" responded, including, later, the Eagle helicopter.

The intruders left the school, but waited nearby and attacked collegiate students as they left school about 3pm.

A St John spokeswoman said an ambulance was called to an incident at Gilbert Rd and Franich St, Ōtara, at 3.24pm.

"We treated one patient in a serious condition and transported them to Middlemore Hospital," she said.

A hospital spokeswoman said the male student was discharged just after 7pm.

Turketo was unable to confirm a rumour that the injured student was stabbed.

"I don't know, it's not that I'm fobbing you off," she said.

"As the principal of the senior school, it's disheartening and sad. It's disappointing because this is our community and I care for our community and I believe in our community."

Turketo said the intruders "came onto our site, so our students didn't leave their classrooms".

"The antagonists were a mixture of students from the neighbouring school and others who were not at that school," she said.

"There was a lot of social media, apparently, so there was a lot of calling in for back-ups."

She did not know how many were involved but said there were "a lot of people".

"I called the police to disperse the antagonists," she said.

"They were good, and they moved them on, and then left - I mean the police left the area.

"The intruders went into the park and it just carried on. After school our students had no choice. As our students came out of the school, they were waiting."

Police again responded.

"I left the handling of the situation with the police," Turketo said. "There were lots of police and the Engle helicopter was involved."

At one stage during the afternoon, Turketo went out to talk with the intruders in the nearby Ngāti Ōtara Park.

"I tried to talk them down and I asked them to come into the school and I said, 'You are welcome to come into the school and we'll sit at the table and we'll talk about it'," she said.

"They said, 'No thank you, we've got it sorted'."

A police spokesman said police "were notified of a breach of the peace incident involving a group of students outside the school around 1.30pm".

"One police unit attended and Eagle was not present," he said.

"Police then responded to a large disorder incident shortly before 3pm. Multiple units attended that incident, including [the] Eagle helicopter."

Turketo, who took over as the school's principal at the start of this year, said she was still trying to piece together all the details of what happened and would speak to students and staff to find out more tomorrow.