Catholic and other state-integrated schools have edged out their elite private counterparts in university entrance (UE) results, with state schools well down the list, new research reveals.
The study by business think tank the NZ Initiative adjusts school performance for students' personal and family characteristics.
The research has been produced in association with a three-part Herald investigation of private schools which begins today.
It finds that, after adjusting for everything the Government knows about every family, you can lift your child's chances of finishing school with UE by 8.3 percentage points by sending them to an integrated school, or by 6.9 points at a private school, compared with attending your local state school.
Students attending state schools between 2008 and 2017 had an average chance of only 30.5 per cent of leaving school with UE.
That increased to 37.4 per cent in a private school and 38.8 per cent in an integrated school.
The differences are statistically significant because of the huge number of 398,961 students across all of the country's 480 secondary schools who are included in the 10 years worth of official data.
However, they measure only one narrow outcome of schooling - UE. The study does not look at the broader National Certificate of Educational Achievement (NCEA) because some elite schools use other exams, such as Cambridge and the International Baccalaureate, instead of NCEA.
UE is the only measure that can be used for all schools because NZ universities accept high marks in Cambridge or the International Baccalaureate as equivalent to an NCEA-based UE.
The NZ Initiative study is the first of its kind to compare academic results adjusted for students' backgrounds and across all types of schooling - a regular point of contention in debates over which schools achieve most for their pupils.
However University of Auckland Professor Peter O'Connor argues that the focus on UE results alone "reduces the complexity of learning to such a narrow construct that it becomes meaningless".
"As a professor of education, I'd fail my master's students on that. It's a false science," he said.
"There is nothing to suggest that going to a private school means you will be happier, lead a more purposeful life, contribute more to the world, have better relationships with your partner or your children. That in fact your life matters for having been lived.
"You might have better connections, even more money, but that isn't much in the grand scheme of life."
Massey University Professor John O'Neill noted that state-integrated schools, which are privately owned but state-funded on condition that they follow the state curriculum, are almost all faith-based.
Almost half (46) of the 99 integrated schools with at least 30 students and including Years 11 to 13, the criteria for inclusion in the study, are Catholic. Almost all the rest are Christian (45), Muslim (2) or Hare Krishna (1), and the other five are Steiner (4) or Montessori (1).
"We know from other research that faith/kaupapa community schools tend to perform better than heterogeneous secular community schools, so it's no surprise if NZ state-integrated schools on average outperform state schools on average," O'Neill said.
"It is interesting, though, that they also have a slight advantage over private schools. Faith trumps dosh?"
Two-thirds of private schools in the study are also Christian, 24 out of 36. But the other 12 are secular, such as the ACG group, Pinehurst School at Albany, Wentworth College at Gulf Harbour and Huanui College at Whangārei.
The study found that private schools have the highest proportion of schools in the top quarter of all New Zealand schools for students achieving UE adjusted for family characteristics - 24 of the 36 private schools (67 per cent) are in that top quartile, compared with 45 per cent of integrated schools and just 15 per cent of state schools.
Private schools also have a higher proportion than integrated schools in the bottom quartile - three out of 36 (8 per cent), compared with 6 per cent of integrated schools. State schools are much higher at 32 per cent.