Prime Minister John Key opened up debate about league tables on Monday, when he expressed support for them, in response to questions at his post-cabinet press conference.
He thought showing a school's progress on National Standards was a better indication of its performance than using a decile status as a proxy for performance.
Mr Key said yesterday that the reason parents were using deciles "as a de facto form of assessment" of schools was because it was the only piece of information they had.
Asked if National Standards information was reliable enough to be the basis of comparison of schools, he said everybody accepted that the information would settle down over time, just as it did with NCEA.
There were some moderation concerns about whether one school was assessing achievement the same as the school down the road or even concerns within schools.
How the information was to be presented was something for the Ministry of Education to work out with the education sector.
NZEI teachers' union president Ian Leckie said league tables would have a severely damaging effect on children's education and would unfairly label schools and students as failing.
"National league tables are a very narrow, simplistic and unreliable tool to assess education achievement and school success. This is especially so in New Zealand where they would, no doubt, be based on dodgy, unfair and unmoderated national standards information."
Labour leader David Shearer said: "The Government's National Standards does not allow one school to be compared against another, and we've said this right from the very beginning. It's not comparing like against like, so I think the idea is really dead in the water."