In a decision to overturn a later suspension of the year 2 child, the ACT Civil and Administrative Tribunal heard evidence the child had been locked in a classroom alone on a previous occasion.

The tribunal found the student should not have been suspended after he allegedly attempted to strangle, scratch and kick other students and began taping a classroom door shut in July 2019 after a period where he had been reportedly bullied.

The tribunal also criticised "tardy and incomplete responses, excuses and explanations by the school".

An internal review by the Education Directorate confirmed the principal's decision to suspend the child, but the father applied to the tribunal for a review of this decision.

The tribunal heard in the lead-up to the suspension, the boy's father had found his son locked in a classroom in April 2019 when he went to collect his son for an appointment.

A school leader gave evidence she had been working in an adjoining room when she heard the child, who said other students were "trying to get him".

The school leader told the tribunal she locked the door so no one could enter but the child could leave if he wanted to. She said she had spent time playing with the boy and did not notice him to be dirty.

The school leader said the boy had been involved in many playground incidents and had shown aggression to other students.

The tribunal was told the child experienced epilepsy, disabilities in fine and gross motor skills and problems with emotional regulation and required a learning support assistant.

Emails from the boy's mother to the tribunal tendered to the tribunal said the student had been unsupervised in February 2019, and in April 2019 he had been kept apart from students for the most of the day.

Another email from the child's mother in April said her son had been "really upset about school and being excluded in the playground".

The father argued the suspension was an inappropriate and unduly severe response to the situation, taking into account his son's age, disabilities and medication, lack of intention and the apparent minor degree of injuries to other children.

He also argued the school had failed to provide proper psychological support to his son during the 2019 school year.

Dr Douglas Jarvis, appearing for the education directorate, argued the lack of psychological support had been the result of action taken by the boy's parents rather than the directorate, and there was little evidence the child had been bullied.

While the tribunal accepted the arguments had merit, there was evidence there had been ongoing issues in the lead-up to the suspension.

"The [preceding period] is too replete with events, complaints by the applicant and his wife, tardy and incomplete responses, excuses and explanations by the school, and similar incidents, for us to accept that there was no underlying problem," the tribunal's decision said.

The principal told the tribunal she made the urgent decision to suspend the student for one day because he had been unable to calm himself down, had been violent to other children and staff attempts to help him de-escalate the situation had been unsuccessful.

She told the tribunal she had decided a break from school was needed to give the student time to settle and allow the school to regroup.

But the school could have arranged for the student to attend school but remain separated from other students or informally requested the boy's parents keep him from attending, tribunal members Mark Hyman and Lisa McGlynn said in a decision published last month.

"The effect of [an informal request] would have been the same as a suspension but without the formalities and the punitive appearance of those formalities," Mr Hyman and Ms McGlynn said.

The tribunal members said the overarching principle of the territory's education act was the right of every child to a high-quality education.

"With that in mind, and taking all the circumstances of this matter into account, we have concluded that the correct or preferable decision was not to exercise the discretion to suspend the applicant's child, but rather to pursue one of the alternatives identified above," the tribunal's decision said.

The principal directed specific questions about the incident to the education directorate, which did not respond before deadline.

However, a spokesman said the directorate was taking the necessary time to consider the important issues raised in the decision.

"The ACT government's future of education strategy includes as a key principle the goal of an inclusive education system. The government recognises that pursuing this goal requires cultural and systematic change that will take time," the spokesman said.

"As part of delivering its election commitments, the government will be working with students with disabilities and their families on how to take steps towards an education system that includes people with disabilities in ways that suits them."

The spokesman said data on school suspensions did not record whether students had a disability.