Parents are paying hundreds of dollars to prop up free school education with one of the country's top colleges asking for close to $1,000, a Weekend Herald survey has found.
Auckland Grammar topped the survey with an annual donation request of $975 a student, well above any of the other 125 schools surveyed.
However, while donations at higher-decile schools have generally increased since a previous survey in 2005, those at low-decile schools - which receive more government funding but often have trouble collecting donations - have remained static, been reduced, or even scrapped altogether.
Schools asking the highest donations blame rising costs - particularly for technology - that are not being met by government funding, with one saying the reality is education is not free in New Zealand.
Donations may be requested from parents, but they can choose not to pay or only pay partly. But schools often put a lot of pressure on parents to pay up.
Auckland Grammar headmaster Tim O'Connor said the decile 10 school did not receive the government funding necessary to maintain its high standards, and parents understood that, with most treating it as a fee.
"The payment of a donation is a sign that you are supporting the Grammar education and the Grammar way ... the use of the term [donation] provides the suggestion that education is free in this country, but the reality is it isn't."
Mr O'Connor said the donation incorporated extracurricular activities which other schools charged for separately.
Epsom Girls Grammar School (EGGS) was second in the survey with a requested donation of $625.
Acting principal Sarah Stenson said government funding was not enough to adequately cover costs and donations were required to hire more teachers to reduce class sizes and invest in IT infrastructure.
Parents spoken to by the Weekend Herald said they understood why donations were going up.
Judith Walker, who has a son at Auckland Grammar, said the donation was well used by the school and she wasn't asked for any other money - but she thought it could be cheaper.
"It's not horrendous, but hitting $1,000 is as much as we would want to go ... I think they could take it down to $750."
Belinda Frederiksens, with a daughter in Year 9 at EGGS, said the donation was justified by the service the school provided.
"You do pay more. But in my view the donation is paying for what is available to my daughter at the school."
However, Labour's acting education spokeswoman, Megan Woods, said local MPs were hearing more complaints from parents about donation levels.
She said the Government's priorities were focused on the private sector, leaving funding gaps in the state sector. A spokeswoman for the Ministry of Education said funding for schooling and early childhood education had increased to a record $9.7 billion a year, and the country's investment in education as a percentage of GDP was higher than the OECD average.
Education Minister Hekia Parata said government spending on schooling had increased 30 per cent since 2008, and schools' operating grants would rise by 1.9 per cent from the 2014 school year, exceeding forecast inflation.
"It is nonsense to say that state schools are suffering at the expense of private schools or partnership schools.
"Of the over 2500 schools in New Zealand, only 85 are private and the state subsidy for private schools has not increased in recent years."
Albany Junior High School saw the largest increase of any school since the last Herald survey in 2005, jumping from $150 in 2005 to $550 this year. Principal Mike Jackson said the needs of students were changing and costs were rising as a result.
"These days a lot of it is around providing ICT equipment in the schools and paying to run the internet."
A report prepared by the Ministry of Education last September found the overall cost was one of the big factors parents - particularly those with lower incomes - looked at when choosing a school. That cost included uniforms, extracurricular-related expenses and a particular focus on donations and fees.
- Additional reporting: Elesha Edmonds
• Schools are free to choose if they ask for donations.
• State schools cannot enforce the collection of donations and cannot penalise students for not paying them.
• Parents can choose to pay, partially pay or not pay donations at state schools.
• State schools must make it clear to parents that donations are voluntary.
• State-integrated schools are allowed to charge attendance dues that are compulsory.