The secondary teachers' union is concerned the National Party's promise to spend $1 billion from asset sales on education is a ploy to camouflage what it sees as harm from asset sales.
The Post Primary Teachers Association says no one would oppose putting more money into education.
The National Party will proceed with the partial privatisation of state-owned energy companies Genesis Energy, Meridian Energy, Mighty River Power and Solid Energy and reduce the Crown's shareholding in Air New Zealand if re-elected on 26 November.
The party has projected that up to $7 billion will be made from partial asset sales, with profits to be spent on infrastructure such as ultra-fast broadband in schools.
But PPTA president Robin Duff hopes the policy is not a cynical attempt by National to gain support for asset sales.
Mr Duff says while any spending in education is good, it needs to be clear whether the $1 billion is in addition to money already ring-fenced for education.
National's education spokesperson Anne Tolley says it is on top of money already allocated for schools and would allow for more investment in education without additional borrowing.