ACT Education has suspended a principal and launched an investigation into how a primary school student was placed in the purpose built two-by-two-metres structure made of metal pool fencing.

It is understood the structure within the classroom was built specifically for the student, believed to be a 10-year-old boy with autism, on March 10. It was dismantled on March 27, the day after the directorate became aware of it.

The Canberra Times has chosen not to name the school to protect the identity of the child.

The government has not told parents at the school of the incident, except for those with children in the school's special needs unit, who were notified in a letter sent by the acting principal.

The letter said: "The school intended that this space provide sanctuary in response to the needs of a student. The space was clearly unacceptable".

A parent of a child at the school, who did not want to be named, told The Canberra Times he was disgusted at learning of the incident.

"I don't think anyone should be locked in a cage," he said. "They are not criminals, they are just children that need help, not to be locked away."

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The child was placed in the structure on at least one occasion for an unknown period as a behaviour management technique.

A concerned member of the school community referred the matter to the ACT Human Rights Commission.

The Education Directorate only became aware of the issue after a formal complaint by the Children's and Young People's Commissioner on Thursday, March 26.

ACT Education Minister Joy Burch announced the independent inquiry on Thursday - World Autism Awareness Day - saying she was horrified and distressed by the incident.

Ms Burch, who is also Minister for Disability, said "Words cannot put into place my absolute disappointment and horror that anyone in our schools would consider a structure of this nature in anyway shape or form to be acceptable.

"Will there be consequences? The investigation will go into that - this is an example of extreme poor decision-making.

"At this stage, we are still clarifying whether the withdrawal space was ever used, and if so, how many times and under what circumstances. That is what these investigations will do."

The student has remained at the school throughout the past week, with Ms Burch saying the school community, the family and the affected child needed privacy.

The principal, meanwhile, has been removed from the school and placed on administrative duties within the directorate. Two senior staff have been placed in the school in the interim with support staff made available to the family involved.

Director General of ACT Education Dianne Joseph returned from leave last week to deal with the issue and said the directorate had put in place an independent inquiry, which was to expedite its findings on the school.

She said it would inquire into "How was the decision made? How was the decision made at the school level and what was the involvement of different people from the directorate? Who knew what when?"

The directorate believed this was a one-off incident and has checked that no other government schools are employing similar withdrawal or behaviour management techniques.

Ms Joseph noted that schools regularly employed withdrawal spaces in order to manage behaviour among students with special needs.

"These spaces can take a range of options and are implemented regularly - they could be a learning support assistant take someone outside for a walk in the school grounds, or it could be a safe reading corner still visible but around the corner," she said.

"They are used fairly regularly across our schools. But the decision-making around the space - because the space was so unacceptable - is in important part of the investigation."

Australian Education Union ACT secretary Glenn Fowler said the union was supporting staff at the school and was deeply disturbed by what had happened.

"We fully endorse a speedy inquiry," he said.

The ACT Council of Parents and Citizen's Association vice president Hugh Boulter said he was alarmed at the news and fully supported inclusive classroom practices across the ACT.

"I understand that the directorate and the minister have taken swift steps in response to this matter, including providing immediate support for the student and the family concerned as well as support for the broader school community. I further understand that the school's principal has been removed and that the directorate have verified that there are no similar or comparative arrangements in any other ACT government school," he said.

He asked that non-government schools also be considered in any ongoing investigation into withdrawal spaces and behaviour management practices.

Opposition Education spokesman Steve Doszpot was briefed on the issue on Thursday afternoon, but questioned why it had taken a week for the minister to announce both the incident and forthcoming inquiry.

Mr Doszpot said the Opposition wanted assurances the inquiry would be "fully independent and held at arm's length from the Education Directorate and Education Minister."