The government has been accused of dragging its feet after only spending less than a fifth of the money promised to address school roll growth pressures in Auckland.
It also needs to complete building 202 classrooms in the next four months to meet its own target announced last year.
In 2014, the government announced it would spend $350 million over four years to build new schools and classrooms - however, in written response to questions by the Labour Party, it said it had spent just $60m.
It has also been revealed that only 75 of the 230 new classrooms promised last year have been completed.
Only five of the 52 replacement classrooms the government plans to have all finished by January have been built.
Labour Party education spokesperson Chris Hipkins said the government had yet again made promises without any commitment to ensure they were delivered.
"They either weren't ready to deliver on it or they were just basically making it up as they were going along.
"We know that there are schools in Auckland that are absolutely cram-packed, they're desperate for the extra classrooms, so the fact that the money supposedly is there and yet the buildings are not showing up - that's really concerning."
He said as the classrooms remained unbuilt, it was the children and teachers who suffered.
"They're either going to be in overcrowded schools or they're going to in really old classrooms that are past their use-by date and are really unhealthy places to be.
"Or it could simply mean that there is no space and that schools are having to convert libraries, or gymnasiums or staff rooms into teaching space, because they've got nowhere else to put the kids."
However, acting Education Minister Anne Tolley said even though only $60m had been spent, around $300m had been committed to projects.
In a statement she said there would always be a delay between announcement and delivery.
"Once money has been committed for a project, there's a process to be followed. It's important to note that building school infrastructure is a complex process, given the various steps from consulting through to design, consenting and construction involved.
"Factors such as the availability of supplies and contractors can also impact on timelines, especially in a burgeoning construction environment such as Auckland."
Ms Tolley said the 175 classrooms and 47 replacement classrooms that had yet to be completed were all in various stages between planning, and design to construction.
New Zealand First's education spokesperson Tracey Martin was sceptical and said there may be a hidden incentive for the government to delay the classrooms.
"They're going to put it through a piece of legislation by next year, that will allow children not to go to a face to face school, but stay at home and actually go online, is that going to save them money and then they are not going to have to build these classrooms?"
The government said it was investing more than any previous government in school infrastructure and by mid next year would have spent $5bn since 2008.