He still suffers night terrors, his mother told the Herald. She plans to lay a complaint with the Ombudsman, and possibly with police.
At least ten other children - both mainstream and special needs - had been locked in the room in the past year, for up to 25 minutes, largely without parent knowledge or consent, the investigation said.
The school says it will phase out the use of the room, and the Ministry has appointed specialists to work with teachers on positive behaviour strategies.
It is the second such incident in New Zealand schools in recent months - the first, when a 13-year-old boy attending a special school was put in a time-out room last year - prompted the development of soon-to-be released seclusion and restraint guidelines.
"We have become concerned about this practice, which is why we brought together an advisory group, including principal and teacher representatives, to develop clear guidelines for schools," the Ministry of Education's head of special education David Wales said.
"We know there are still a number of schools around the country that do occasionally use these rooms, and Miramar Central has been one of them. However schools are not obliged to report to us on the use of such rooms."
He said the law doesn't specifically prohibit the use of time out rooms, but the ministry view was that it was an extremely serious intervention, and schools should work towards phasing it out.
A spokeswoman for the Office of the Children's Commissioner said they were not directly involved with the family in this case, but seclusion in schools was an issue the Commissioner was concerned about.
"We'll be talking more with relevant agencies to work out whether this is a wider systemic issue and if we need to take further steps," she said.
Head of Autism Action NZ Kimberley Hall said she believed the Ministry of Education need to implement policy, not guidelines, around the use of seclusion.
"Parents entrust schools with their children's physical, emotional and psychological well being. This is a massive breach of trust with extremely vulnerable children," she said.
"There also needs to be a greater understanding of the behaviour of children with autism and education for staff around how to deal with it, instead of treating them like they are deliberately being naughty."
The school plans to send a communication to its parents on Monday about the situation. It has accepted the findings of the investigation, Miramar Central School Principal John Taylor-Smith said.
He accepted the room was "outmoded" but said it had only been used for very extreme behaviour - when students were a danger to themselves or others.
