The term "long tail of underachievement" was coined in 2007, by former Secretary for Education, Karen Sewell. However the knowledge of the disparity had been around since the early nineties, when the demand for unskilled workers had faded away, and it became clear the system was not serving everyone the same.
More recently, PISA data showed that New Zealand's gap between the pass rates of rich and poor was one of the widest in the world. Latest figures show it's still there, despite the rise in achievement figures at a national level.
Successive governments have sought the silver bullet for underachievement at significant cost. Many low-decile schools have nurses, social workers and food-in-school programmes. Charities donate raincoats and shoes to pupils.
The Government pays for teen-parent units, trades academies and military-type training. Billions of dollars have gone to early childhood education. And, of course, there is extra funding targeted by decile to "level the field".
"The idea of deciles was good," says Dr Vicki Carpenter, an education researcher at Auckland University and the author of Twelve Thousand Hours: Education and Poverty in Aotearoa New Zealand. "But somehow it hasn't managed to achieve what we hoped it would."
It is popular for politicians to blame much of the underachievement on teachers and teaching. Policies are usually aimed at professional development or targeted at lifting cultural response.
Critics have identified key areas where the system is weak: the decile funding model; the number and types of interventions; the lack of ability to attract and keep quality teachers and leaders in low-decile schools; and what they say is a "failure" to address the underlying issue of poverty.
Reinventing the wheel
A major criticism of the education sector is that there is too much re-invention of the wheel. With each political cycle, a new government wants to stamp its mark, claiming conquest.
At one point, Papatoetoe High School principal Peter Gall counted 25 policies running at once, and said the system was suffering "initiative-itis".
A second concern is that interventions are dumped for the wrong reasons. The Literacy Professional Development Project (LPDP), for example, was considered a turning point for teacher practice, deemed successful by its designer Helen Timperley because of its deep roots in research. Asked why it was discontinued she writes: "I can only say 'democracy at work' and decisions about a change of direction within the Ministry of Education."
Te Kotahitanga was deemed too expensive. Part of it was rolled into a new policy, called "Building On Success", aimed a cultural awareness for teachers of Maori students. However, Te Kotahitanga's architect, Professor Russell Bishop, says in doing that, the programme lost what made it work - the intensive evaluation of in-class teachers.
The chief researcher at the New Zealand Council for Education Research, Cathy Wylie, says there is also a pattern of expecting schools to carry on initiatives without extra support, or ensuring the right leadership is in place first.
Wylie is hopeful about some current projects. PB4L, a behaviour programme, is having some success. Schools sharing knowledge through Communities of Schools also has potential, she says.
Quality teaching and learning
Research shows low-decile schools can struggle to attract and retain staff. In 2012, the Child Poverty Action Group recommended action towards addressing the issue.
Secondary Principals Council chairman Allan Vester believes teachers in low-decile schools should also be paid more, with better student-teacher ratios.
Robin Staples, principal at Southern Cross Campus in Mangere, said the school spent some of its decile funding on extra teachers, and if it had more money, would employ more. The school staffed its after-school programmes and Saturday workshops with volunteer time.
Although the Government has introduced a new professional body - the Education Council - to raise the status of the profession, it has yet to adopt specific measures for teachers in low-decile schools.
Much of the policy aimed at lifting achievement is targeted at better cultural understanding of Maori and Pasifika students. All the experts spoken to believed blaming ethnicity for underachievement was also very convenient.
"An equally obvious explanation is surely poverty and the fact that Maori and Pasifika students are over-represented among the poor," Massey University professor of education John O'Neill said. "Governments cannot reasonably choose to focus policy on only one of two important contributing values."
While schools could improve assessment outcomes, he said, research showed attempts to close the gap by focus on classrooms or schooling alone were "insufficient."
Not everyone agrees. Education Minister Hekia Parata repeated in Parliament yesterday that schooling factors collectively had a much greater impact on student achievement than home background, despite Ministry of Education-funded research to the contrary.
She told the Herald that was why the Government was focusing on lifting the quality of teaching and school leadership and making it easier for schools and teachers to share expertise and resources.
"Some low-decile schools are achieving exceptional results. We want all schools to achieve exceptional results."
However, Waikato University education professor Martin Thrupp said that so far, policy based on exemplary cases had not always worked well. He was concerned that unless poverty was addressed, the inequalities would remain for another 50 years.
"I think the problem is that if you say it's over to the schools and not social inequalities, you will keep just looking for the silver bullet," Professor Thrupp said.
Teaching kids tricks of the middle class
Manurewa High School principal Salvatore Gargiulo has spent the past year teaching the kids at his South Auckland school how to be more like the middle class.
"I told them, look a person in the eye when they talk to you," he says. "And then the local Countdown manager said to me, 'What's wrong with your kids? They're all staring me down,' and I realised they may have taken it a bit too far."
Mr Gargiulo believes it's vital for kids from disadvantaged backgrounds to learn what he calls the "hidden rules", and not because he wants them to disavow their own culture.
"In a lot of ways how these kids think is better. They care more about each other than possessions, for example.
"What we're trying to do is teach them how to get along in a society they know little about."
Research from the United States says the resources students in poverty need aren't just financial, but social and cultural. The knowledge the middle class take for granted may be far from their experience.
This year, Mr Gargiulo has departed from his maths class on regular occasions. Lessons included filling out tax forms, getting a drivers' licence and how to save on a water bill.
"I got my class to research borrowing $2000 on personal loans - not one thought of going to the bank," he says. Instead they found websites charging astronomical interest.
Mr Gargiulo, who is retiring this year, now wants to help embed the lessons into schools nationwide. "And it's not just about the kids, it's about teachers learning how these kids think. Perspectives and attitudes are different and it's important to understand that."
Numbers paint desperate picture
Decile funding is designed to bridge the gap for students who have less. It provides up to $1000 per student extra, but research has found high-decile schools maintain the ability to fundraise twice that from parents and international fees.
Low decile schools are often smaller, their facilities dated, and extra-curricular offerings can be limited. At decile 1 Mangere College, for example, students can choose from 10 sports. At Rangitoto College, a decile 10 school, students have 40 options.
Mangere's principal, John Heyes, shows us around the school - a low, concrete block facility built in the 1960s. Tapa cloths hang on the wall, and a poster reads "how to make a healthier meal with mutton flaps".
Students are mostly Pasifika. Year 9 health checks pick up undiagnosed issues like sight problems, and 20 per cent have the reading levels of students four years younger. Yet their Pasifika student pass rates outstrip some of their higher decile neighbours.
The school relies on grants to help send Year 12 students to camp, or the volleyball team to national champs. This year, the juniors have been saving for their trip away - about one in four will be able to front the $150. If the school had more money, Mr Heyes would like to pay for the rest of the students to go too. He'd also bring in a device for every kid.
Heyes is retiring at the end of the year. What else would he have liked to do? He thinks for a moment: "Recently the student council revised the uniform - the girls were desperate for long, pleated skirts. But when they realised the costs of a pleated skirt would be prohibitive for their families they did away with it. I would love to be able to give them a pleated skirt."
At Rangitoto College, principal David Hodge takes us through his budget. This is a school where students go on trips to Germany and Japan, where the dux was accepted to Harvard last year.
The school brings in $2 million a year in international student fees and $400,000 in parent donations. Despite that, Mr Hodge said, there are huge pressures - particularly around staff numbers, where a government formula not designed for very large schools sees them down about 20 full-time teachers a year. He said the expectation on the school was huge.
"We here are in the most fortunate position that we can be, and are able to bridge the funding gap. But there are a lot of schools that can't do that because circumstances are stacked against them," he said. "Funding should not be done on an out-dated model. It should be needs-based."
By the numbers
Targeted funding, annual
Parent donations, annual
$0 International student fees, annual
Six students went to Samoa
$0 Targeted funding, annual
$425,000 Parent donations, annual
$2,000,000 International student fees, annual
Parents pay Sports
Overseas trips Japan, UK, Turkey, Germany
1 water-based hockey turf
Yesterday: A day in the lower deciles: We go inside some of our poorest schools
Today: The long tail of the long tail: Why does the underachievement gap persist?
Tomorrow: What is working:
A simple idea helping bring families and schools together