International students are paying tens of thousands of dollars to attend New Zealand state schools - funding that is crucial to lessons, teacher development and other support for locals.
Some schools have more than 300 international students with up to $20,000 a year charged for lessons that are - bar "voluntary" donations - free for local students.
But that income could be put in jeopardy by increasingly fierce competition from other countries and New Zealand's slide on international education league tables.
Increasing international students have become a key way for the tertiary sector to fund itself, but less attention is given to school enrolments.
One Auckland secondary school brings in around $3.2 million each year from international students, and says limited funding means the money is essential to keep it running.
Primary schools are also actively recruiting international students, with "extras" such as school technology and play equipment funded by the enrolments.
Rangitoto College principal David Hodge said many New Zealanders did not realise how crucial international students were to both the economy and school budgets.
"It's one of the least-known but most dynamic export sectors in New Zealand ... simply put, without the income from international students the school's ability to provide an education of the level the community expects would be impossible."
Rangitoto is the biggest school in the country with a roll of about 3000. It has a benchmark of around 230 fulltime places for international students, but because some study for only a semester or term total numbers can reach up to 350.
Fees are $15,000 per year, with a total gross income of around $3.2 million a year. After costs, including marketing and additional teaching staff, about $1.65 million is invested in the school for the benefit of local students.
Mr Hodge said income from international students impacted on every aspect of the decile 10 college, including allowing specialist classes, more support for students with special needs, and professional development for teachers.
International students would also pay to stay with homestay families, and spend thousands of dollars more during their time in New Zealand.
"The kid that has come to New Zealand is not then buggering off to Tahiti to spend their money in the weekend, they're spending it here on goods and services."
There were a total of 15,287 international student enrolments at New Zealand schools in the first half of 2013, latest available figures show.
Numbers have remained relatively steady since 2009. However, that does not convey the often rapid rise and fall of student numbers from different countries.
Primary school enrolments dropped by 9 per cent in the last reporting year, mostly because of a steep drop-off in student arrivals from South Korea.
A decline in birth rates, the shrinking of the middle class and a drive by the South Korean Government to retain its own students by improving local education, particularly English language provision, are all factors.
However, strong growth from markets including China and Thailand has helped soften the decline - if South Korean students are excluded from the picture primary school numbers grew by 12 per cent.
Owen Alexander, principal of Takapuna Normal Intermediate School, said a drop in South Korean students at his school had been offset by more from China. He said Italy, Brazil and Malaysia also contributed students.
Takapuna Normal had 21 international students paying $14,000 a year, and joined with other local schools to market "pathways" through the school years.
"The international market has become more important to funding the developments in New Zealand education generally."
Malcolm Milner, principal of Balmoral School in central Auckland, said the fees that his 10 international students paid unquestionably helped.
"The education budget is tight. It just means you can do more for your children in your school - that's the bottom line."
All the international students at Balmoral lived with their own relatives.
"We have a family from Saudi Arabia. The Saudi Arabian Government has paid for the parents to do their masters out here. One [Japanese] family we have here fled during the earthquake. The father still works in Tokyo and the mother and girls live out here."
Like all schools spoken to by the Herald, Mr Milner said the benefit of international students was not just monetary but also the diversity they added to classrooms.
Commentators have forecast an increase in demand for international education globally, however, at lower levels than previously predicted.
Education NZ is a government organisation with the primary role of student recruitment and as a marketer of New Zealand as an education destination. Its chief executive, Grant McPherson, said there was optimism that international numbers could grow in the coming years.
However, there were challenges and the competition for those willing to pay top dollar on their child's education was intense. Countries that have provided much of the growth in student numbers have pumped hundreds of millions of dollars into improving the schools and education opportunities available to their own citizens. And with the effects of the global economic downturn still lingering, those students who do go overseas are increasingly looking to countries within their own region.
"Traditional competitors are getting stronger, but what you have is new competitors coming forward. Students in countries that might have travelled to New Zealand to learn English can actually learn English much closer to home," Mr McPherson said.
Adding to the scramble has been the establishment by brand name British private schools of satellite operations, or franchise partnerships, in countries such as Thailand, China, South Korea, Singapore, Kazakhstan and Qatar.
New Zealand's Academic Colleges Group (ACG), which runs the private ACG Parnell College, Senior College, Strathallan, and Sunderland schools here, has bought land in Bali, Indonesia, and will soon build a new school there.
ACG already has successful international schools in Jakarta, Indonesia, and Ho Chi Minh City, Vietnam, educating a total of around 1500 students.
"It's a mixture of children of wealthy locals, blended marriages and expat children," said Kim Harase, ACG's associate principal and director of marketing. "There is a demand for quality private international education."
The heightened competition is being felt by other countries, too - the most recent figures show international student numbers in Australian schools fell by almost 4 per cent over 12 months.
Mr Hodge said countries had realised they would need to fight for their share, and New Zealand was up against "well-funded campaigns" run by Canada, Australia and Britain.
When New Zealand was revealed to have fallen down international league tables in the Programme for International Study Assessment (Pisa) report late last year, there was much wringing of hands about the implication for Kiwi students. But Mr Hodge said the implications of such a public drop in rankings for New Zealand's fifth largest export were hardly discussed.
"You can imagine if a story had come out to say that the wine industry has been suffering a blight in terms of a major bug ... everyone would have been going, what's the economic harm?
"Well, education is a far bigger industry than wine. The Government certainly does, but the country as a whole don't have a mindset that this is an incredibly important business."
Mr McPherson said Education NZ's view was that it was still too early to tell what effect the Pisa results might have, but there were other factors that influenced a student's decision on where to study - and they were largely in New Zealand's favour.
"Quality [of education] is definitely one. And New Zealand is seen as having high quality ... and there are other things around relative safety, lifestyle, and environment."
Most international students in New Zealand pay to stay with local families (Auckland Grammar students pay $260 per week). Mr McPherson said this was another strength of the system here. However, there were issues with supply.
Southland was one region looking at building hostel-type accommodation for school-aged international students, and that might be part of the solution.
He said the economic benefits to New Zealand were considerable. International education in schools had a gross output of $361 million in 2012/13. Further, having a "studied in New Zealand" alumni that increased by thousands of students each year would bring further benefits as those students grew up and took up positions in their own country's business, government and wider society.
"It actually captures a piece of their heart," Mr McPherson said. "It sounds a bit naff, but there's an emotional connection, when the piece of time you have had here actually influences what happens in your life."
Chilean teens getting to know the way things are done in NZ
An almost 100-strong group of Chilean teenagers studying in New Zealand schools are enjoying their time here-but there are aspects of the Kiwi character that take some getting used to. When members of the group, who are split among 47 schools around the country, reunited recently they were grateful to greet one another with some South American warmth.
"We're happy when we get to see each other at events. Here people don't touch. When we meet again, we were all hugging," said Claudia Ortiz de Zarate, who is spending six months at Botany Downs Secondary College with countryman Juan Uribe Barros.
The Chileans are unusual for international students here because their Government is paying for their fees and stay as part of its "Penguins Without Borders" scholarship scheme.
The top-performing students, known as "penguins" because of their distinctive black and white uniforms, went through a rigorous selection process and are marked as future
The secondary school sector has seen strong growth resulting from South American scholarship schemes. Last year, 334 students from Brazil arrived under a similar programme.
Sergio Gonzalez and Evelyn Henriquez met the Herald to share their experiences of New Zealand so far, which were overwhelmingly positive.
There had been some homesickness for the 16-year-olds, who were living away from home for the first time. But the warm welcome from their host families and fellow students meant the transition had been smooth. The diversity of New Zealand schools was a major difference commented on.
"We can learn about a lot of cultures," said Sergio. "It's a really good opportunity to make myself independent ... I have to do things by myself. It's a really good experience to make myself stronger."