Staff at one of eight special schools that have used seclusion rooms to discipline children have refused to talk to police investigating a family's complaint.

Photo: RNZ / Alexander Robertson

Education Minister Hekia Parata revealed today that eight of New Zealand's 64 special education schools had used the rooms.

And she told Checkpoint with John Campbell she was "surprised" to learn that staff at Invercargill's Ruru Specialist School, which is at the centre of a police investigation relating to the use of restraint and seclusion, had invoked their right to stay silent.

The investigation was launched after the parents of a profoundly autistic child complained about his treatment.

Neither the school nor police would comment.

But an email from the police officer in charge of investigating what occurred at the school, which was sent to the child's parents, said the investigation was nearing completion.

He also stated that staff had "elected to invoke their right to silence which means no interviews will be conducted by police", and he could not tell the parents when the door had been removed from the seclusion room, because no questioning of staff was permitted.

Ms Parata told RNZ she had not heard of any teachers invoking their right not to talk to police, and she was surprised that staff at the school had chosen that option.

Eight special schools found to have used seclusion rooms

Ms Parata told Parliament this afternoon her ministry made the discovery that eight special schools had used seclusion rooms after reviewing special schools around the country.

She understood seven of the eight rooms had been used this year, she said.

She had made it clear to those schools that the use of the rooms was unacceptable.

The Office of the Ombudsman has also been investigating after receiving complaints about at least two schools confining children, including some with autism, in small rooms.

Last week it emerged that Miramar Central School in Wellington had been confining children in a small dim room in response to behaviour such as hitting, biting, kicking, choking and slapping.

In the separate case involving Ruru Specialist School, the nine-year-old autistic boy was restrained and transported by van to a seclusion room.

The incident happened in 2011, but it was three years before his parents were told.

A report commissioned by the ministry into the boy's confinement found that, although not illegal, the use of such rooms in special education schools was common practice.

Ms Parata said the eight schools she talked about today did not include Miramar Central School.

A sector working group was developing guidelines on better restraint and behaviour management practices, she said.