'He's extremely lucky': Teen allegedly stabbed outside Waikato school

St John and the Waikato Rescue Helicopter responded to a serious assault outside the school. Photo / Supplied

A teenage boy allegedly stabbed by another student as he was leaving school yesterday afternoon is "extremely lucky" to be alive after the knife missed one of his key arteries by just millimetres.

The 16-year-old is recovering in a ward today at Waikato Hospital after undergoing urgent surgery last night.

The boy's father told the Herald his son "was out of the worst", but the whole family had been left shaken by the incident.

The boy had just left a Waikato school at 3pm and was heading to his mum's waiting car when a 15-year old schoolgirl confronted him.

The boy's father said his son tried to ignore the girl as she approached him and told her to "go away", but she caught up with him before allegedly stabbing him with a knife.

"It [the knife] missed just by millimetres the main artery from taking blood away from the liver," the father said.

"It was just extremely lucky to be honest ... just lucky it was someone that didn't know what they were doing."

The knife had been plunged into the front of his body, damaging four organs including his lung and liver.

The boy's mother had been standing about 4m away and a teacher from the school was also nearby when the alleged attack happened.

"No one realised what had happened until a minute later when she threw the knife away and then everyone realised what happened," the father said.

The boy's mother quickly piled her son into her car and drove him to a doctor.

St John attended and the Waikato Rescue Helicopter flew him to Waikato Hospital in a critical condition.

"He wasn't in a good way when he was getting to the hospital so he went under the knife straight away," the father said.

After spending a night in intensive care, the boy was transferred to a ward earlier today and is expected to spend five days in hospital. He then faces a further three-month recovery at home.

The father said he had not heard from the school which appeared to be keeping its distance while police investigated.

"At the moment it's not their problem because it happened outside the gate, it's a police problem."

The boy's family was now "hiding away" as they did not even know whether the girl had even been suspended from the school after the incident.

"I always thought I lived in paradise, but this has just changed my life completely."

The boy had been home-schooled at the end of last year after tensions between him and the girl surfaced. The father said they decided it was better to keep him away from any further accusations.

His son had only just returned to school at the start of this term after he and the boy's mother met with teachers and were given reassurance about safety procedures and promised the students would be kept apart as much as possible.

A school spokeswoman confirmed an incident happened just after 3pm on Wednesday.

Police were investigating and the school was not able to make any further comment at this stage.

The school had reopened today and plans had been put in place to support students and staff.

A police media spokesperson said the inquiry was ongoing.