A new survey suggests strong opposition to the idea of private companies being involved in the development and management of new schools.
The New Zealand Educational Institute commissioned the study in which 60 per cent of respondents were against the idea of allowing private developers to build, own and operate school buildings and lease them back to schools.
National has said it is examining an Australian scheme that allows public-private partnerships in the development of schools.
NZEI president Frances Nelson said the union wanted public education in New Zealand owned, operated and funded by the Government.
"Schools' ability to undertake teaching and learning should not be compromised by an outside party such as a private developer."
Ms Nelson said there was a fear private developers would put profit first and bring uncertainty into education if they pulled out or sold off schools.
National released its infrastructure policy this week but did not give a solid signal on its stance on schools.
National education spokeswoman Anne Tolley said there were no plans for private companies to develop and manage schools under National but it could be possible.
She said the party was focused on good education for children.
Education Minister Chris Carter said other countries that tried the model had encountered problems with developers scrimping on features to save money.
How strongly do you support or oppose the proposal that would allow private developers to build, own and operate school buildings and lease them back to schools?
* 8% - strongly support
* 10% - support
* 18% - neutral
* 13% - oppose
* 45% - strongly oppose
* 6% - unsure