The Ministry of Education has investigated every complaint it received about child-sex offender Robert Burrett, the minister says.
Education Minister Hekia Parata dismissed opposition party calls for an independent inquiry into what they said was her ministry's inaction over a Christchurch sex offender.
Labour and the Greens were accusing the ministry of not acting on complaints about Robert Burrett, who will be sentenced next month for sexually abusing a dozen girls, aged between five and 12.
The school that flagged concerns over Burrett two years before his arrest said changes were needed to protect disabled children.
Burrett had been a teacher and principal at several schools around the country before working in Christchurch as a school caretaker and then a contracted bus driver for special needs children.
The Board's chair said the school would be meeting Ministry of Education staff next week to talk about changes needed to safeguard disabled children.
One idea was to have an extra person on buses carrying disabled children.
The chair said the Ministry had proposed cameras and GPS tracking of buses but that wouldn't stop children being offended against.
Labour Party spokesperson for education Chris Hipkins said an independent inquiry could look into how much the ministry knew about Burrett's behaviour.
"Clearly the Ministry of Education were given a lot of information - some of which they acted on and some of which they didn't," he said.
"I don't think that's good enough and I think that we need to take a very close look at why all of the alarm bells weren't ringing much, much earlier and action wasn't taken much, much earlier."
Green Party education spokeswoman Catherine Delahunty supported an inquiry to ensure the ministry took a stronger stance in the future.
"When there are several schools over a period of time raising the alarm when we thought we'd fixed this through the law - we clearly haven't.
"So the systems aren't working sufficiently to pick up when somebody is causing alarm and people are not being heard by the ministry so we do need to look at this."
But Ms Parata said she had been assured the ministry investigated every complaint it received about Burrett.
Ms Parata said the case was an operational matter for the ministry, the police and the school transport provider.
However the case highlighted the importance of recent changes to child protection laws and how the Education Council operated, she said.
Those changes included making it mandatory for concerns about teachers and principals to be reported to the Education Council.
Concerns raised about Burrett in 2013
Ministry of Education head of sector enablement and support Katrina Casey said the ministry had not received any information about allegations of sexual abuse in terms of previous schools Burrett worked at.
"In terms of Burrett's past employment in schools, we are not and were not the employer of Burrett in these cases and we can only ever act on information that we receive. Schools are independent self-governing entities, and employ their own staff."
However, Ms Casey said the school Burrett was employed at in May 2013 had raised concerns with the Ministry, alleging inappropriate comments and behaviour.
She said a transport operator interviewed Burrett and provided notes of the investigation to the parents.
"The parents accepted Burrett's account and asked that the investigation be cancelled.
"The school advised the transport operator, Ministry transport service agent and parents that they were pleased with the process followed and that the matter had been resolved.
Ms Casey said the transport operator also chose to move the driver to a different route so that he did not continue to drive the student.
If at any stage the parents or the school had been unhappy with the investigation or its outcome, the Ministry would have become involved, said Ms Casey.