UPDATED 2.43pm The death of a Napier schoolboy strangled trying to jump out of a locked toilet cubicle has been described as an avoidable tragedy that should never have happened.

The coroner has delivered a scathing report into the death of Aryan Banerjee who died in September last year three months after he was found hanging from a window latch at Taradale Primary School in Napier.

The 9-year-old had gone to use one of the Taradale school's toilets but ended up locked in the cubicle because the handles had been removed.

With no way of opening the door, Aryan climbed backwards out the window, but his shirt became entangled on the latch as he tried to jump free.

Coroner Tim Scott said Aryan's death "could and should have been avoided".

Although he has not made any formal recommendations Scott has written to the Ministry of Education to suggest a new style of toilet doors in the wake of the death.

Mr Scott said the school caretaker was in the middle of urgent repairs to fix the door handle and had left for three to five minutes to get tools.

However, Mr Scott said he must have been longer than that, with no real urgency demonstrated to get the job done.

He said access to the bathroom was not blocked, no warning signs, cones or tape were in place, although they were available.

Critically, the manually operated catch was off the lock in the door.

Mr Scott said the caretaker should have spotted the risks. Two other children had previously been trapped in the toilet, including the principal's own child.

Mr Scott said it was "also foreseeable that Aryan would attempt to escape via the window".

"On the balance of probabilities, [the caretaker] should have foreseen as a consequence what actually happened."

The simplest and most obvious way of preventing the toilet from being used was to close the door. "That is all that is needed to have been done," he said.

Mr Scott said the caretaker had been significantly affected by what happened and was regarded as competent by the principal.

The man, who has name suppression, is still on school staff and has not faced disciplinary action.

Police and Worksafe have not laid any charges.

The coroner did not make any recommendations, saying they may be unworkable.

Instead, he has suggested that all school toilets should have stall-type doors, with a gap at the bottom, and windows that can fully open, in the hope of avoiding a repeat.

However, Education Ministry deputy secretary Jerome Sheppard says the Building Code doesn't allow schools to make such changes.

He said the Ministry will provide the findings to all schools, and revisit their design guidance.

The boy's father Dr Anjan Banerjee said he's happy with the findings.

"I am very pleased with the way the inquest went and I'm glad that it wasn't Aryan's fault, which is the most important thing."

Mr Banerjee welcomed the coroner's suggestion to use stall-style doors in school toilet cubicles. This provided an emergency exit if something led to pupils being trapped.

At the time of the inquiry, the ministry permitted full doors on toilets and these were still being used in the primary school where his son had his dreadful accident.

Taradale Primary School's refusing to comment on a Coroner's report into the fatal strangulation of one of their students.

Board of Trustees chair Steve Alexander said the school continues to agree with the WorkSafe investigation, which found the caretaker's actions were not foreseeable.