Kiwi parents and other private funders are paying more for schooling than in almost all other OECD countries.
A new report has found NZ is third only to Colombia and Turkey when it comes to the share of the national income that parents and other private sources contribute to schools.
However, the Government is also paying a considerable amount.
The figures, reported in the latest Education at a Glance update by the 36-nation Organisation for Economic Cooperation and Development (OECD), reflects high spending on our schooling.
New Zealand's total taxpayer-funded spending across all levels of education was 5.5 per cent of our national income, the seventh-highest in the OECD.
At the same time nearly 18 per cent of NZ schools' funding comes from parents and other private sources, compared with an OECD average of 10.3 per cent.
NZ Ministry of Education deputy secretary Dr Craig Jones said the report showed that New Zealanders are well served by their education system overall".
"However, the high-level nature of the indicators used within Education at a Glance hide the huge amount of variability within the NZ education system, which is our greatest challenge," he said.
Post Primary Teachers Association (PPTA) analyst Rob Willetts said the high private share of funding in New Zealand was a measure of inequality between schools.
"The bigger the private contribution to the education system, inevitably the greater the inequity," he said.
"If you look at a high-decile school in the leafy suburbs where the parents are providing significant additional funding to the school, and you have a lot of overseas students pumping in a lot of additional funding, then the education experiences of a kid in that school are so far ahead and so much broader than the educational experiences of a kid in a school in a poor community."
Willetts said New Zealand's high total spending on schools as a share of the national income also reflected our younger population than most advanced economies.
However, despite our higher spending, NZ class sizes are slightly bigger than average - 17 students per teacher in primary schools compared with an OECD average of 15, and 15 per teacher in secondary schools compared with an average of 13.
NZ teachers were paid only slightly above the OECD average relative to all tertiary-educated workers in 2017.
Primary teachers earned 86 per cent of average tertiary-qualified workers against an OECD average of 84 per cent, and NZ upper secondary teachers earned 95 per cent of the tertiary-qualified average against 93 per cent across the OECD.
OECD measures of student outcomes put NZ 15-year-olds still in the top half of advanced nations, although trending downwards: sixth in science, eighth in reading and 16th in maths.
But a test of primary school reading levels put NZ children only 22nd out of 41 countries in 2016.
Ministry of Education data shows that state and integrated schools get 87 per cent of their funding from taxpayers, plus 7 per cent from parental donations and other "local funds", 2 per cent from foreign students and 4 per cent from hostels, investments and other sources.