Radical changes are needed to New Zealand's schooling model to stop the success of wealthy schools at the expense of the poor, education experts say.
Data shows decile 10 schools, those with the lowest proportion of disadvantaged students, are now an average 2.5 times the size of an average decile 1, with the highest proportion of students from low-income families.
In Auckland, some of the so-called "top" schools have doubled in size in the last 15 years, while a cluster of low decile schools have seen their rolls halved in the same time, as parents "choose up".
The impact of the exodus was made clear in the recent Herald documentary Under The Bridge, set inside decile 1 Papakura High School, where falling student numbers saw staff cuts, disused classrooms and a sense of pessimism about the school's future.
"When I first started. I would walk through the gates everyday and it was basically packed," said former Year 13 student Robert Downes, 18. "At lunchtimes ... it was packed and now ... nothing. Basically ghosts. You could yell and you'd hear yourself echoing."
Principal John Rohs, who began his role in 2016, said many students in the school's catchment either left to attend Rosehill College, the higher decile school across town, or bussed elsewhere each day.
"It's something I find really disappointing," he said. "That the Papakura community doesn't have the confidence that Papakura is a good place to be educated."
However Rohs said it wasn't just the community to blame - the longer he spent at the school the more he realised it was poor planning at a government level as well.
"It doesn't seem to me that anybody really at ministry level thought through clearly over the past 20 years what the picture of education in Papakura should look like," Rohs said.
"It just seems like a jumble of ad hoc decision were made that allowed one school to become enormous and one to become small," he said. "It's been a really predatory environment."
He said while relationships with schools were warming, it wasn't enough to overcome the years of muddled thinking and competition, or the schooling model.
In New Zealand the Tomorrow's Schools structure sees each school managed at a local level, with parents able to choose which school their children attend - adding an element of competition for the "best" schools.
Some schools have zones, meaning those inside that area have the right to attend that school. Most take a certain number of "out-of-zone" students as well, which can be sought-after places.
Educationalist Bernadine Vester, the author of the new book South Auckland, Southern Transformation, said if there was to be a better chance for students at low-decile schools, the competitive element needed to be better managed.
"We need to move to Tomorrow's Schools 2.0," she said. Proposed changes to funding - which will see decile ratings scrapped - and the introduction of "Communities of Learning" - where schools are enabled to work together - was not enough, she said.
"What we need to change outcomes for kids in communities like Papakura is a change to the status quo."
Vester believes there should be a regional body for each district that sits between the Ministry of Education and individual school boards, to ensure decisions made by schools are best for everyone in the community.
The suggestion is similar to one made by chief researcher Cathy Wylie from the New Zealand Council for Educational Research in her book "Vital Connections" five years ago.
"You need someone who would be able to sit down with principals and look at demographics and what money is available, and find the fairest way to provide schools of good quality for every student," she said.
That might mean some restrictions on parent choice, although that would be unpopular.
"This is why you have a central government that is prepared to make hard decisions," she said.
"As a system we are trying to improve education for everyone, with taxpayer money. To do that most effectively we have to provide choice in a way that isn't going to make it harder for others."
Education Minister Hekia Parata said she believed every child should have access to a great education to support them to fulfil their potential and achieve more in life.
However she thought the changes already proposed by the government would provide the necessary update to Tomorrow's Schools to allow for more collaboration and a more targeted equity funding system.
In particular, she said the Communities of Learning would shift the focus to student pathways rather than individual institutions.
"It is the difference between schools competing for roll size and education providers collaborating in an organised and systematic way in the best interest of all children," Parata said.
More than half of all schools and all kids were now part of a Community, which were required to set achievement challenges as a group and would receive funding to meet those challenges accordingly.
A funding review is ongoing.
• Average decile 10 school is now 2.5 times the size of a decile 1
• Since 2000 in Auckland, some high decile schools in Auckland - including Mt Albert Grammar, Macleans College, Western Springs - saw their rolls almost double in size.
• Meanwhile, the low-decile schools haemorrhaged numbers. At Edgewater College in the city's east, the student muster halved in a decade. Kelston Girls lost 400 from its roll, Glenfield College 600.
• Almost no other school felt the impact of the exodus as severely as Papakura High. By 2016, the roll dwindled below the 600 mark.
• Achievement at those schools is also lower.
• Statistics from 2014 showed that although overall achievement levels were rising, particularly for Maori and Pasifika, children at deciles 1-3 were four times as likely to leave with no qualifications as those at deciles 8-10.
• Just 17 per cent of low decile children got University Entrance in 2014, compared to 60 percent of high decile.