More children have come forward with complaints against a teacher who this week admitted 49 charges of sexually abusing pupils - and police say they are stretching back their investigation to the mid-1990s.

Commissioner Larry Forbes, who was appointed this month to Pamapuria School near Kaitaia, said that since James Parker's identity was revealed on Wednesday more children had contacted authorities.

"I'm not aware of how many or where they've come from, but I understand there have been more and I understand there's a strong possibility that there are more to come. But numbers I don't know."

Parker, 37, was a teacher and deputy principal when he committed the offences against boys in his care.

Most of the 49 charges related to offences since 2009, but police yesterday told the Weekend Herald their investigation would stretch back to the mid-1990s.

That comes after a former principal revealed she had complained about Parker to police when he was a first-year teacher. She was concerned that he was sharing his own bed with pupils during "sleepovers" at his house, among other things.

Her claim was backed by an ex-pupil of Parker's who said he had children over for sleepovers and shared tents with them on school camps.

She said it was well known in the community that the principal had approached police to make a complaint about Parker.

Police said there was "no record" of any complaints from the principal or from children about Parker in 1996.

Spokeswoman Annie Coughlan said: "As a result of the current charges, police have received information from teachers referring to concerning behaviour during his teaching years including from the mid-1990s.

"Those reports, including whether police were notified at the time, now form part of the continuing investigation."

The ex-pupil, now a grown woman who still lives in Kaitaia, said Parker was "extremely trusted".

"He embezzled his way into people's lives and made himself part of their families. Everyone trusted him, absolutely everyone. But [the principal] raised these concerns on many occasions," she said, speaking on condition of anonymity.

When the charges against Parker became public the former pupil was "shocked, but not surprised".

"It's disgusting. When [the principal] brought it up all those years ago, masses of parents turned against her. She got shunned and pushed out of the community. I felt extremely sorry for her."

In Kaitaia District Court this week Parker was convicted of sexually assaulting 12 of his students between 2004 and 2012.

After his appearance it was revealed that police had investigated allegations against Parker in 2009.

They interviewed Parker and a number of students but could not substantiate the claims against him. After the investigation, police wrote a "strongly worded letter" to Pamapuria principal Stephen Hovell, saying it was inappropriate for a schoolteacher to invite young children to his residence to sleep over.

Most of Parker's offending happened after that letter was sent. Mr Hovell is out of the country and has yet to comment on the saga.

But his son David Hovell spoke out in his defence yesterday, angry at those who had criticised his father.

"I'm making this statement off my own back because I'm sick of people who don't understand my father's character and in some cases have their own agenda, making untrue accusations and misleading the public," he said.

"The reason my father is not speaking up is that he's been told he's not allowed to speak to media and that all questions should be referred to the school commissioner. He would love to be there supporting the school and community but it's outside his control. Anyone who knows him personally knows that of course he would put the children's welfare above everything else."