The parents of an autistic child are furious at the Minister of Education's claim she only found out about seclusion rooms in July, because they complained to her about the same issue a year earlier.

The controversial rooms, described as cell-like, were the subject of a series of complaints at Wellington's Miramar Central School.

Today, Hekia Parata announced plans to outlaw their use.

But when the news broke about Miramar Central School, a Southland family sent Checkpoint with John Campbell letters to and from Ms Parata about the same issue at a different school.

The family first wanted to remain anonymous, but have broken their silence, speaking exclusively to Checkpoint.

After announcing her proposal to ban seclusion rooms, Ms Parata was this morning asked a very specific question: Was July of this year the first she had heard of schools locking children into seclusion rooms?

"Yes. And at that time, I did not know, however, that [the room in Wellington] was a seclusion room. I knew that there had been a complaint by a parent, I knew that the ministry had commissioned an independent investigation. And then the report came in, in October."

But Southland mother Victoria Turnbull wrote to the minister in May 2015, raising serious allegations about her autistic son's treatment at Ruru Specialist School in Invercargill.

Specifically, that her nine-year-old had been restrained and transported to a seclusion room at the school, and held for up to 12 minutes at a time without their knowledge.

"We wrote to the minister because we had addressed the issues with the school, and the board, and we felt we were getting absolutely nowhere."

That was May 2015, 16 months ago.

A month later, in June 2015, Ms Parata replied.

Mrs Turnbull's letter to the minister explicitly used the phrase "seclusion room".

Asked about Mrs Turnbull's complaint, Ms Parata stood by her statement that she had not heard about seclusion rooms before July.

She said the room at Ruru was deemed not to be a seclusion room.

"I am saying that's not what the investigation found in the report, and I am also saying that the term 'seclusion' was used very loosely over the past year or two.

"What we have now done is define specifically what it is and ruled it out."

Room was never locked, school management told investigator

The report into Ruru Specialist School, carried out by Terri Johnstone on behalf of the Ministry of Education, said school management denied the door had ever been locked.

She described the room as dark and grimy, said the atmosphere was unpleasant, and called the use of the room inadequate.

Ultimately, Ms Johnstone's report of February 2015, some 20 months ago, recommended the school close the room.

Mrs Turnbull said what she saw at Ruru School was barbaric.

"It was heinous. It had concrete walls, concrete floor, no windows, it was dark ... Since the ministry have investigated, there are windows at the ceiling point.

"Solid door, solid walls, and no way to get out."

Minister stands by response

Ms Parata told Checkpoint the room at Ruru Specialist School was not the same as the room being used at Miramar Central School.

She didn't agree with what had happened at Ruru, but said the term "seclusion room" and its definition had been inconsistently applied in the education sector for some time.

That was why an advisory group had been set up - to establish consistency across the sector, she said.

The parents who wrote the letter to the ministry about Ruru School had not been ignored, she said.

"The investigation was commissioned when we got the complaint in December 2014, the ministry acted on that investigation and the practice was stopped."