James Parker was able to continue his offending against young boys for so long partly because of his close relationship with the principal and his authority as deputy principal and kapa haka leader.
That is one of the findings of a report into the former deputy principal of Pamapuria School, 10km south of Kaitaia, who is awaiting sentencing on 49 sexual abuse charges.
He was due to be sentenced on November 15 but that may be delayed due to fresh complaints since his crimes became public.
The report aimed to find out why the school failed to keep its children safe and what can be done to prevent other cases in future. It is separate from the ongoing police investigation.
It found warning flags had been raised several times since Parker started teaching at Oturu School in 1998, including his habit of showering with boys staying at his home or sharing his bed "marae-style" .
Sometimes unusual behaviour was accepted because Parker had an adult girlfriend, so people assumed he was safe with boys. Others thought he was not a risk because children stayed overnight with parents' permission.
Parker's closeness to some families and his mana as kapa haka leader made it hard for people to accuse him.
Others felt their concerns would not be acted on because he was close to principal Stephen Hovell, the report says. Before 2012, the closest Parker came to prosecution was in 2009 when a boy's mother went to the police. Two other boys were named as victims.
However, one boy said nothing had happened and the two others later retracted their allegations.
Detective Dean Gorrie, of the Kaitaia CIB, could not lay charges but wrote Mr Hovell a stern letter, saying Parker's habit of having boys sleep over was inappropriate, highly unprofessional and had to stop immediately.
It was not clear whether the letter was read in full to the board of trustees, which was given only limited information by Mr Hovell, according to the report. The report also said the trustees' response to the 2009 investigation was overly focused on Parker's welfare and he was not formally warned about after-hours contact with children.
Mr Hovell had been approached with concerns about Parker by another deputy principal in 2008 and a trustee in 2009.
There was, however, no evidence he knew of the earlier concerns at Oturu School.
The report was ordered by commissioner Larry Forbes, who is now in charge of the school.
He described Parker as a "master manipulator" who manipulated situations and relationships to commit his crimes.
Mr Forbes said the report was thorough and objective. It would help Pamapuria School and, hopefully others, learn from "this dreadful experience" so it did not happen again.
"The crimes were committed and we can't undo that, but it would be another crime not to learn from what happened."
The report's "quick-fix" recommendations had been implemented already, while others, such as lifting the self-esteem of children and their ability to report abuse, would take longer.
Other recommendations include training staff to recognise abuse, a system to log after-hours contact with children, and more rigorous processes for appointing teachers.
Mr Hovell declined to be interviewed for the report.