Sites earmarked for Auckland schools have been sold off for almost $20 million in the past two years, with much of the land going to housing developers.
Information released under the Official Information Act to Labour shows four sites marked for educational use were sold since February last year, two on the North Shore and two in South Auckland.
Some sold for more than 200 times the original purchase price.
A block in Totara Heights was bought in 1984 for $170,000 and sold to Fletcher Housing for $5.5 million in December. A 2ha bush site next to two primary and intermediate schools in Browns Bay was bought for $30,000 in 1970 and sold to a developer for $6.6 million.
A site initially put aside for a primary school in Long Bay is to become a reserve, and land in Weymouth is to be a special housing area, with a proportion of affordable homes.
The Ministry of Education says the land was in areas where it was sure existing schools had room to cope with population growth.
Proceeds went back to the ministry, or where the land was part of an existing school - as in Browns Bay - half went to the board of trustees.
Details of the sell-off follows revelations about the sale of school houses across the country, and high school land sales in Massey and Tamaki for residential development.
Labour education spokesman Chris Hipkins said the sales were short-sighted.
"In some cases they're selling off land that was bought to future-proof for growth," he said.
"There are already areas that have significant population growth where we haven't thought ahead and are having to pay massively inflated prices - if we sell these sites now a future Government is going to have to shell out millions more when the population moves again."
The sales come as schools in Auckland are filled to bursting point, with an extra 200 classrooms announced last month to deal with a rising population expected to produce 107,000 more pupils over 30 years.
A $350 million government plan will see nine new schools built with the profits from asset sales, as well as two- or three-storey blocks to protect playing fields to ease the pressure on swelling rolls.
Two of those schools have been announced - primary schools in Kumeu and Scott Pt - and add to five recently built schools.
Ministry infrastructure service head Kim Shannon said the sales had been in parts of Auckland where schools had room for projected roll growth, and where existing schools could add classrooms.
"We have bought land in other parts of Auckland experiencing rapid population growth, and where existing schools won't be able to cater for that growth," she said.
Population projections for the areas where the land was sold off - Browns Bay, Long Bay, Weymouth and Totara Heights - showed some of the areas have already experienced growing rolls.
Long Bay College, for example, added 500 students to its roll since 2003, and the population in the area is expected to grow five-fold by 2030.