She said parents should have received counselling and advice within 24 hours of getting a letter telling them the offender had been in contact with their children.
More effort should have gone into supporting parents than into breaking the news to media, she said.
"We've had all our children at risk and we'd like that to be dealt with and we think that should have been foremost...
"At the moment it feels like we've been left out of the conversation."
Parents who feared "the worst" wanted to know how to talk to their children about what contact they may have had with the offender, the advocate said.
She said vulnerable parents may have panicked in the day after learning about the offender.
The man, who is now in custody, has been given two extended supervision orders, which are reserved for sexual offenders with a high-risk of re-offending, and which imposed release conditions preventing him from associating with people under 16 or from working without the approval of a probation officer.
He had dodged authorities for years by using more than 10 aliases and was arrested in South Auckland a week ago.
He has since appeared in the Auckland District Court on charges of breaching release conditions.
There is no indication at this stage of him illegally engaging with pupils as a teacher.
The names of the schools that may be affected cannot be published, but the man was convicted in 2004 for three acts of indecent assault and two acts of assault against his 14-year-old nephew.
He was found guilty of skin of skin touching and punching his nephew in the head. The sentencing judge noted the man's abuse of trust and the degree of force used to overcome his nephew's protests. He was found not guilty of sexual violation.
He was sentenced to two years' jail and released in 2005 on an extended supervision order. But the order could not be served on the man because he disappeared, and was not located again until August 2009. During that time he had used more than 10 aliases, changing his name by deed poll.
He is understood to have had 77 criminal convictions - mainly for dishonesty and disobedience - and he lied to the Corrections Department psychologist by giving her the name of a school and principal as character references that did not exist.
Last week a school referred the man to the police after learning he had used multiple identities.
Prime Minister John Key said it was a huge concern that a number of government agencies failed to pick him up.
"We'll frankly rip the system apart and work out what went wrong and why ... We know he is a fairly devious person, obviously, but we don't know exactly why the system's failed to pick him up, and it's absolutely critical we restore that confidence."
Teachers are registered through the NZ Teachers Council, which includes a police check on applicants based on information supplied by council.
Education Minister Hekia Parata said the teacher worked at two schools, and possibly a further six.
She said the man was due to reappear in court next month.
Authorities lambasted
A parent of a child at one Auckland school where a convicted sex offender worked for more than two years is "massively concerned" at the systemic failure that lead to the situation.
The man, speaking to the Herald on the condition of anonymity, said he had a daughter at the school.
"The biggest issue is there has been this letter and then absolutely no contact about how the hell we deal with the situation with our kids, from the Ministry of Education or from the school," the parent said.
"My immediate disbelief is around the complete unpreparedness of the ministry for dealing with this situation that parents are facing now."
He also found it concerning that the letter parents received from the school did not say anything about the former teacher's conviction.
In a letter to Education Minister Hekia Parata, the parent asked why qualified advisers had not been offered to help parents. "Why are you all over the media wringing your hands about a situation you have known about since late last week?"
- Additional reporting: Andrew Koubaridis
