His son suffered a blow to the back of his head during the incident he described as a "riot".
"On the back of his head he has a lump the size of an egg," he said.
The father had since taken his son to see his doctor, who he says deemed him unfit to go to school until next week.
The father was waiting to pick up his sons from the college just after 3pm on August 15 when he got a call from the school to say his youngest son had been involved in an incident.
"They told me he was all right, he had just been in an incident."
He said he had later found out from his son that a group of students had entered school grounds at lunchtime after "wagging for the day" and approached a group of younger students.
"They weren't in school uniform," the father said. "They took a basketball and wouldn't return it."
The father said when his son went to get the ball back he was "punched in the back of the head and smashed into the wall".
The father believed the whole confrontation continued for about an hour as students "were running around hunting for kids to bash them up".
Katikati Police Sergeant Steve Hindmarsh said police believed "the fracas started after a misdirected ball struck another student".
Police were investigating a complaint made by a parent of one of the students who was allegedly assaulted in the incident.
Hindmarsh said police were not called at the time because staff had quickly intervened.
However, he said a police officer went to the school later that day to escort a student, who was believed to be involved, back home.
Katikati College Board of Trustees chairman Peter McCormick said five students were directly involved in the incident as well as 18 students who were "indirectly" involved, meaning they were there at the time of the fight.
"We are using our behaviour procedures to deal with those involved and as a result it was necessary to suspend a number of students."
McCormick said the situation "accelerated" and staff needed to be called in as well as the police for one student.
"The school are working with the students and their parents as well as the Ministry of Education to ensure there is not another incident such as this.
"The school has put processes in place to ensure the health and safety of all students and staff at our school."
Ministry of Education deputy secretary of the enablement and support sector Katrina Casey said a member of the public called a community meeting on August 17 in response to the altercation.
Casey said ministry representatives attended the meeting at the request of the principal and addressed questions from the public.
"We will continue to provide support to the school and the community, and are committed to work alongside the Board of Trustees and principal to best serve the needs of student and staff welfare."
