High-decile schools in Auckland are taking in millions of dollars more in non-government funding than the rest of the country, helped in part by international students.
Annual report figures show the city's high-decile state primary and secondary schools and mid-decile secondary schools made more on average per student from non-government sources than comparable schools in the rest of New Zealand last year.
Auckland principals deny the extra funding is giving them an advantage, arguing that they face higher costs than other regions.
The figures provided by the Ministry of Education show Auckland state secondary schools in deciles 8-10 received an average of $2655 per student in non-government funding last year, $680 or 34 percent more than the average for decile 8-10 schools in other parts of the country.
State primary schools in Auckland in deciles 8-10 received $946 per student from non-government sources, about $275 or 41 percent more than schools in other parts of the country.
The figures from the ministry included most, but not all, state schools. RNZ's calculations do not include integrated schools which are able to charge extra fees for property and special character. They also do not include government funding because all state schools are funded on the same formula.
International students appeared to be behind the relatively high incomes of Auckland's high-decile state secondary schools. The schools received less from donations and activities than schools in the rest of the country on a per-student basis, but about twice as much from foreign students ($1186 per student compared with an average of $540).
The city's high-decile primary schools received $276 per student in donations, about $90 more than any other part of the country, and $167 per student in foreign student fees, more than three times the average of $45 for high decile schools in the rest of the country.
In other decile groupings, the figures were more varied.
Mid-decile Auckland state secondary schools received $1848 per student in non-government income last year, nearly $200 more than the average for the rest of the country and their per-student income from international students of $793 was more than double the average for the rest of New Zealand.
Auckland Primary Principals Association president Heath McNeil said many of the city's schools might receive more non-government funding than schools in other areas, but they also faced higher costs.
"Getting a plumber in costs more in Auckland than it does in other regions," he said.
"There's an understanding in the higher-decile schools in Auckland that it does cost more to run a school in Auckland because of those outside costs."
Mr McNeil said he would not describe the schools as advantaged and they faced parental demand for specialist teachers in areas including the arts, sport and music.
"There's no separate funding for that from the ministry so one way that high-decile schools can ensure that they're meeting community expectations is through international students or higher donations," he said.
Auckland Secondary Principals Association president Richard Dykes said it was difficult to make comparisons between groups of schools without knowing more about factors such as the state of buildings and the city's schools facing "incredibly high" recruitment costs.
He said many of the city's schools received less operational funding from the government on a per-student basis than other schools because they were large and the funding formula assumed they would make savings.
"You don't get economies of scale in education. It's a myth," he said.
"For us the fundamental question is, what is the level of education that our community wants and what does it actually cost to provide that and the figures that you've provided indicate that it costs a heck of a lot more - in some cases even up to twice as much - as what the government is actually funding."
Macleans College in Auckland reported the single highest income from fees last year at $5.65 million. The school's principal, Steven Hargreaves, said most of the money was from international students and it was essential.
"If we didn't have the income from international students we'd be in a world of trouble. They represent about 40 percent of our income," he said.
Mr Hargreaves said the school used the students' fees to pay for 30 extra teaching staff and to contribute to a major rebuild of the school, which was replacing leaky buildings.
"Without the international students, we would have a very bread and butter offering. Straight off the top, we'd be saying goodbye to 30 teachers that allow us to teach subjects we wouldn't be able to offer otherwise, we'd have bigger class sizes, we'd have less learning support, and definitely in that extra-curricular area there'd be much less on offer," he said.
Mr Hargreaves said Auckland schools appeared to find it easier than schools in other areas to attract students from China and South-East Asia, and they also appeared to be able to charge more - about $19,000 per student compared with about $15,000 in other parts of New Zealand.