"The school had failed to follow its own procedures, and acted unreasonably in using the room for a purpose it was unfit for. Record keeping was incomplete and unclear."
Boshier also criticised the Ministry of Education for failing at the time to provide schools with unambiguous and up-to-date guidance on why and how to avoid using seclusion to manage difficult behaviours; guidance it has since sent to all schools.
The report was part of a broader investigation into the use of "time out" rooms in schools, prompted by revelations about a boy who was locked in a cupboard-sized space at Miramar School last year.
The law has been changed to prohibit the use of seclusion in schools.
Boshier said that although the law change did not alter what happened to their child, the parents involved in the Ruru case were "instrumental" in its development.
The report outlined how the boy's parents first complained to the school in 2014, when they discovered their child had been placed repeatedly in an area he called "the little room".
Built in 1999 with ministry approval, the room was designed to help de-escalate children's behaviour such as kicking and yelling, or throwing themselves on the ground.
The investigation found the boy was placed their at least 12 times - but possibly more as record-keeping was poor, the Ombudsman said. He was transported there in a van, and physically placed in the room, the report said. Although the door was not locked, he would have been unable to leave.
Despite being part of school behaviour management policy, the boy's parents were not told about it when their son started at the school, and said had they been aware of it, they would not have enrolled their child at the school.
They described the room - which measured 1.3m x 1.8m - as "barbaric".
The Ombudsman said it was "uninviting" and "unpleasant" and that it was unsuitable in location and for the purpose it was used for.
Using the room for the boy's behaviour was "unreasonable", he said, and the parents should have been told about it.
He said the ministry did the right thing by closing the room while it investigated, but it gave ambiguous advice on seclusion rooms and took too long to formulate guidelines after the issue arose.
"The recommendation that the Ministry convene a working party to develop national guidance was acted on. However, that recommendation was made in February 2015. The working party convened for the first time in June 2015, but it was November 2016 -
18 months later - before the guidance was issued." he said.
"But for the media attention from early October 2016, it may have taken still longer."
The Ombudsman recommended Ruru provide the boy and his parents with an apology "for its failings".
He also asked for copies of the school's current policies and procedures for incident reporting and the use of physical interventions to transport students, and a report on its most recent audit of behaviour management plans.
"Ruru, the Ministry, and the Education Review Office have made a number of changes as a result of this complaint. I will be following up with Ruru to confirm that the improvements I expect to see around its procedures for behaviour management and for physical interventions with students have been made", he said.
