A year-long study has found there are no significant differences in performances between schools of different deciles.
The analysis of data for 400,000 students over the past decade was undertaken by the privately-funded New Zealand Initiative.
The finding calls into question the assertion of the Tomorrow's Schools Independent Taskforce, which has claimed the "quality of our schools varies significantly".
The research looked into the effect school may have "over and above certain different family circumstances", NZ Initiative Chief Economist Eric Crampton explained on TVNZ1's Breakfast this morning.
"Parents are always looking at NCEA league tables or decile rankings or the local rumour mill to try and figure out which schools they might want to send their kids to, but all the different ranking exercises that are out there really mixes up the effect that a school has with all of the effects of the family circumstances that the kid brings with them to the classroom."
Data collated by Statistics New Zealand’s data lab, examined by the New Zealand Initiative, found that once they "separated out all of those family circumstances", they found that "most schools are performing very comparably to one another".
He said the task force's research "is predicated on a few anecdotal accounts" and should not be viewed as fact.
"They went across a few schools, they talked to people there and they found what they saw to be substantial performance differences."
But the new study, Mr Crampton said, looked at 400,000 students who went through NCEA through the past decade and "statistically adjusts for all of the different family circumstances", including their parents' education, income, employment and benefits history, and reports from Child, Youth and Family - now Oranga Tamariki.
"The average contributions across schools? Very similar to each other – even more interestingly, we see some really top performers among low-decile schools that you wouldn’t see on a standard league table.
"People are drawing the wrong conclusions out of different performances across NCEA, across different schools."
Mr Crampton added that the discrepancies between low- and high-decile schools are being exacerbated by parents sending their children to schools outside their local area due to the NCEA league tables.
"You see those differences on the standard NCEA league tables for high-decile schools, always the star performers and low-decile schools perform poorly on average, but once you separate out the effects of the different family circumstances that people bring into the classroom, there are star performers in decile one that are simply not being recognised.
"We're always beating up on decile one schools with a big stick because they don't do quite as well on raw NCEA league tables, but they are performing - a lot of them - admirably, given the circumstances they face.
"We need to have information like this going down to every parent so we stop having parents have their kids walk past the local school to the higher-decile school because they see these NCEA league tables."