The ministerial inquiry was launched after it was found the man - who has a number of aliases and name combinations - was able to teach at several schools despite being convicted for three acts of indecent assault and two acts of assault against a 14-year-old nephew in 2004.
The man is said to have taught at an Auckland primary school from 2009 to the end of last year.
Last November he was interviewed for another teaching position at an Auckland high school and began working there in January.
It is understood his role involved teaching a number of students with special needs atthe school when he was found out last week.
A parent, who has a child at the high school where the man taught, said she had been distressed to find out that a sex offender had been teaching there.
"My child had been taught by that teacher and initially had come home to tell me ... 'my [subject] teacher has been arrested'.
"I said, 'I beg your pardon?"'
"She said, 'Yes he has - I've got a letter for you about it'.
"She pulled it out of her bag and I was just gobsmacked.
"Clearly there's some ginormous cracks somewhere that this bugger fell through and it needs to be sorted out."
The primary school has sent a number of newsletters home this week, explaining the situation as well as giving advice as to how they should speak with their children about it.
The high school has also sent a letter home to parents.
Yesterday as parents arrived to pick up their children at the Auckland primary school where the man had worked, many did not want to comment as they had been asked not to speak to media.
One parent however told the Herald she and other parents in the class were "totally shocked".
The mother, who did not want to be named, described him as an inspirational teacher and a role model who had the parents' full trust and was very much loved by students.
"Clearly this was a man who was good at hiding his tracks. He fooled a lot of people.
"We trusted him fully. We were like a family ... that's why it hurts so much.
"Everyone's shocked."
- additional reporting Yvonne Tahana and Elizabeth Binning.