A Waikato teenager was rushed to hospital with serious injuries after being attacked at school, just hours after he tried to defend another student who was being bullied.

The Herald understands the boy spent several nights in hospital after being kicked and punched in the head during the attack, which is now being investigated by police.

"The final blow was a punch to the head that knocked him unconscious," a parent of a boy who witnessed the attack told the Herald.

"When he came around he was struggling to breathe and couldn't feel his feet at first. He was also disorientated."

The school he attends can't be identified to protect his privacy, and that of the boy responsible, if the case ends in court action.

The school's principal confirmed several students were involved but said he couldn't give any details about what happened or the circumstances leading up to it.

The concerned parent said last Tuesday's attack appeared to have been in retaliation for the teen trying to protect another student who had learning difficulties and was being bullied earlier in the day.

It happened at the end the top of a stairwell just after 3pm and several others students were also indirectly involved, some of whom appeared to be trying to hold teachers back as the boy attacked.

"He hit him, got him on the ground and just carried on and was kicking him and punching him," said the parent.

"I think he stopped eventually but by that stage [the boy] was not in a good way and needed to have hospital treatment."

"The kid that knocked him out ran away afterwards."

A St John spokeswoman said an ambulance was called about 3.15pm last Tuesday. The boy was taken to Waikato Hospital in a serious condition.

The parent said the boy has since been released from hospital but the extent of his injuries are unclear at this stage.

"He was up there for a few days but as far as I'm aware they don't know the extent of the head injury yet. He's a nice kid, he would stand up for anyone - he's known for that."

He believes up to seven boys, aged about 14-15, that were involved.

"I've been told quite a few of them have remained at school whereas only a couple have been stood down while they do their own internal investigation."

The parent is now calling upon the school to expel the boy saying he fears for other students if he were to return.

"It should not happen, you don't send your kids to school for that to happen.

"I think he should be expelled, you can't condone that behaviour."

The principal wouldn't confirm how many students were involved but said there was "a range of involvement from students and the school has responded on a case by case basis to those depending on the level of involvement".

He said the response has varied from offering "supportive measures" to disciplinary action.

"The ministry has been involved and are notified every time we take a disciplinary response and the police have opened up an investigation and we support everyone who is involved in that investigation.

"In terms of the outcomes of any disciplinary hearing that is always to be private and confidential and treated as such so it's difficult for us to go into any details."

He wouldn't be drawn on who called the police or when besides saying they were "on the scene very promptly".

The principal said the school doesn't tolerate bullying and support is being offered to students who need it.

"We engage with our students and our community to have a no tolerance of bullying and to try and address the issue and resolve it."

A police spokeswoman confirmed police were called to reports of an assault at the school on June 29, just before 4pm.

"The matter is currently under investigation and will undergo youth process. Therefore, police will not be providing any further comment at this stage."

The Ministry of Education is not actively involved.

"They have not requested our support at this stage but we are available if needed," said Helen Hurst, deputy secretary sector enablement and support.

Hurst said schools are not required to notify the ministry but they do have to have clear policies and procedures in place to respond to unacceptable behaviour at school.

"Bullying is a complex issue and usually has multiple causes and can take many forms. Where it occurs in or involves a school, it can very rarely be addressed with a single 'one-size-fits-all' response," she said.

She said support is available for the school to manage challenging behaviour if needed.

Youthline said bullying often comes up in calls from young people - be it victims or people who are concerned about someone who has been bullied.

"We really try and encourage them to reach out to any trusted adults," said Youthline's acting clinical consultant Bridget McNamara. "In school context we really encourage them to tell a trusted teacher or school counsellor.

"Bullying is not okay and it's definitely something we can support people with."

WHERE TO GET HELP:

• Lifeline: 0800 543 354 (available 24/7)
  • Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
  • Youth services: (06) 3555 906
  • Youthline: 0800 376 633
  • Kidsline: 0800 543 754 (available 24/7)
  • Whatsup: 0800 942 8787 (1pm to 11pm)
  • Depression helpline: 0800 111 757 (available 24/7)
  • Rainbow Youth: (09) 376 4155
  • Helpline: 1737