Principal Phil Palfrey said he and the board of trustees were horrified by the incident.
"We're making sure the victim and anyone involved are supported through this," he said.
Palfrey couldn't specify how those involved had been dealt with but said the school was moving on from the incident by "doing what we always do".
"We're making sure we abide by health and safety regulations and support our students to make sure they do too, and make sure our teaching is a high standard.
"We have an assembly soon and I'll be talking to the children about the behaviour that will not be tolerated.
"It really just alarms me that our society in general thinks any behaviour like this is in any way acceptable and people viewing it over and over again is somehow healthy."
Palfrey said there were a lot of good things happening in the school too.
"We are committed to making a change for kids in this area to have a better life and that's what I'm going to do. I will never give up, we'll make sure this place is a great place for kids and we're doing everything we can to make it better," he said.
Palfrey said the school reiterated its values of respect, resilience, responsibility and excellence at every assembly.
A letter sent to parents on Sunday on behalf of Palfrey and board chair Lucy Epapara, said the staff, principal and board of trustees had "zero tolerance for this type of behaviour".
"The instigators of this incident were dealt with swiftly and firmly as soon as such behaviour came to our attention," the letter said.
"We would like to reassure and remind our parents and students that such behaviour is unacceptable at Kaitao Intermediate and that both staff and the board continue to work hard to ensure that bullying has no place in our school."
The letter referred to the incident as a "serious assault".
