Teacher unions are stunned at Prime Minister John Key's sudden support for "league tables" of primary schools, warning the data will be "unreliable".
Mr Key says parents are "desperate" for a way to measure school quality and league tables created by the Ministry of Education could be the best solution.
Principals' Federation president Paul Drummond agrees it's important for parents to have the information, but tables built from inconsistent national standards data would be "misleading".
"If parents want to know about the performance of their school or others, they can go to the (Education Review Office) website and look up the school evaluation reports now," he said.
"They can be assured that the information they find is truthful, in context, based on multiple factors and fair."
New Zealand Educational Institute president Ian Leckie was "astonished" by Mr Key's comments.
"The previous minister of education gave the sector and public assurance that the government would not be promoting league tables, and she said that when national standards first came up," he told NZ Newswire.
"Once again, this indicates a change in policy, a change in decision, a u-turn by the government ... It's quite unbelievable, really, how policy can go backwards and forwards."
Education Minister Hekia Parata denies it's a flip-flop.
"It depends on what you're defining as `league tables'. We have always said that we want good quality data and information in the public domain so that parents and schools know how learners are doing," she said.
It was not yet known what form the published data would take.
The tables - which teacher unions strongly oppose - have come up again because of a report that the decile ranking system is causing a drastic drop in the number of Pakeha children attending schools in poorer areas.
The decile rankings depend on the socio-economic circumstances of communities, with decile one the lowest and decile 10 the highest.