"Why are they not putting a school like this in Epsom? I think some honest answers are needed."
He said models overseas were ineffective; Stanford University research showed students at only 17 per cent of charter schools did better than at traditional schools.
It was likely private groups such as McDonald's Ronald McDonald House charities and churches would be interested in the model locally, Mr Duff said.
Mr Duff said that since charter schools could make up their own curriculum under the scheme, it was possible that commercial products could be incorporated into school exercises - such as french fries in maths problems.
"The commercialisation is obviously an aspect of concern. And to move off the national assessment and nationally moderated system and to make something of [the school's] own, leaves them capable of all sorts of distortions."
He said education choice was already offered by smaller schools that had been privately set up, the only difference was now private schools would have access to state funding.
The PPTA would not take any action against the proposal at the moment he said, "although that's under constant review."
Mr Duff said he was still hoping National leader John Key would realise charter schools were a mistake and revoke the policy.
He said the PPTA would not recommend charter schools as an employment option to teachers.
The education sector union NZEI Te Riu Roa was concerned there had been no indication of the policy leading up the election, said president Ian Leckie.
"It is astounding that this sort of policy, which has the potential to change the face of New Zealand's education system, is being arrogantly pushed through and given priority, without the public having a say on the matter."
"We need to be asking why we want public money going into privately run charter schools when there is no evidence they will add any value or benefit New Zealand's education system or local communities."
The Teachers Council urged caution on the model.
"Charter schools are a response in a small number of American states to raising achievement levels in poor urban centres," said director Peter Lind.
"Unlike New Zealand, which has had a highly devolved school system since 1990, governance of schools in the USA is still very centralised and bureaucratic. Tomorrows Schools changed that system in New Zealand over 20 years ago.
"This local governance in New Zealand has brought welcome community involvement into our schools but it hasn't solved the issues of underachievement of some groups of children."