"My initial thought was, 'it's a decile 3 - oh, shit, that is not good.' What on earth have we done?"
The Trevellas decided, though, it was short-sighted to judge schools by their decile rating. The ranking is intended to determine how much additional public funding a school needs - not, as some use it, a predictor of student achievement.
A trip to nearby decile-3 Oranga Primary School soon calmed the couple's fears. With a modest roll of 310, they have decided it is just the kind of community-focused school they would be happy for Phoebe, now 2, and their new daughter Sylvie to attend.
"We got caught up in this middle-class angst about decile ratings that seems to grip a lot of people," Louise says. "The local primary had a glowing ERO report, is well resourced and we like the attitude of the teachers and kids.
"We know a lot of people who have sent their children to a nearby Catholic school as it is in a higher decile band, but we didn't want to have to create a religion for ourselves just to get our kids into a certain school.
"Ideologically, that didn't sit well with us. We want our children to have the same sense of community and belonging we had when we were growing up."
School decile ratings have not been reviewed since the last census, in 2006. This year's data collection was delayed two years by the Christchurch earthquake - meaning a lot of information being relied on is now massively out of date and, frankly, shonky.
The Ministry of Education has told the Herald on Sunday that school decile ratings will be reviewed next year and related changes to funding will be applied in 2015. When the ratings are updated, teachers and parents will be in for a shock.
Since the 2006 Census, property values in many previously unfashionable city suburbs have rocketed, bringing an influx of wealthier residents.
This means decile ratings at many mid-table suburban schools, particularly in Auckland, are certain to rise - and that means less funding from the government. Increased school donations and more reliance on fundraising by parents to make up any shortfall is sure to follow.
The flipside, of course, is that other schools - likely to be in provincial New Zealand or the more deprived parts of the cities - will drop down the decile rankings, and need more public funding to keep their doors open.
When choosing a school it is no surprise that parents get confused.
There are ERO reports, National Standards data, NCEA tables and zones to consider. It is little wonder some people turn to the handy decile rating as a quick - and dirty - guide to the quality of the school.
The Ministry of Education insists that parents should not use decile figures or property prices as an accurate guide to performance or status. Last year, the Education Review Office also decided decile ratings will no longer be included on its school reports.
Dr Graham Stoop, chief review officer for the Education Review Office, said the decision was made because of public confusion about the purpose of the decile rating. It "has no part to play in our reports".
"By removing the decile rating from ERO's reports, we hope to help remove this element of confusion and correct this misconception."
Decile rating figures are arrived at by examining five criteria: Household income, occupation, household crowding, educational qualifications and welfare benefit levels.
Property prices are not a factor in the decile ranking calculation, but clearly, they are a crude proxy for income. Richer people can buy more expensive houses than poor people.
In Auckland, the booming residential market recently pushed 10 new suburbs into the $1m-plus club - bringing the number to 17 in total. House prices have ballooned in up-and-coming suburbs such as Westmere, Ponsonby, Kohimarama and Grey Lynn.
Hayden Duncan, chief executive of national real estate chain Harcourts, says being close to desirable schools is still a main deciding factor in how much people will pay for a house.
It's a giddy upward spiral. Parents pay more for properties near high-decile schools, perceived as being of a better class. As a result of the wealthier, more educated families on the role, the school's decile rating is increased.
Duncan believes schools in emerging Auckland suburbs like Mt Roskill, Glen Innes and Glendowie are certain to see their decile ratings rise accordingly when new figures are released.
"I would expect decile ratings of schools in areas that have become fashionable since the last census to rise significantly, even dramatically," he says. "House prices may not be the measure used for setting decile figures but they are still a very good indicator of how wealthy an area is and this will certainly affect the school decile ratings."
REINZ figures show the New Zealand neighbourhood where median house prices have risen the most since the last census is Oranga, on the southern slopes of Auckland's One Tree Hill. Yes, that's where the Trevellas live - and if the property prices are any indication, their preferred primary school could be in for a shock.
Oranga property prices have nearly doubled from a median of $391,250 in 2006, ahead of the last Census, to a hefty $730,000 this year. The number of families signed up to benefits at the nearby Onehunga Work and Income office has also increased slightly in the same period, so the data is not conclusive - but the best indications are that local schools are likely to climb the decile rankings.
Decile-3 Oranga School will likely be adjudged decile 5, 6 or 7 next year - and accordingly, its public funding will plummet. Louise and Penn Trevella may find they are forced to reach deep into their pockets to pay the "voluntary" school fees. Weekends will be spent on cake stalls and working bees.
Over on Auckland's North Shore, solo mum-of-three Elaine Thomson, 46, is dreading an increase in the decile ranking at the school her sons attend.
Beach Haven used to be a mainly working-class area, in the shadow of leafier neighbouring suburbs like Birkenhead and Northcote.
But Thomson, who has lived there for 18 years, says house prices have doubled in Beach Haven in the past decade, following an influx of upwardly mobile professionals. A recently-introduced direct ferry service to the city centre is another drawcard for wealthier newcomers.
"I'm getting sick of rich people coming here and dragging the area up," she says, only half-jokingly.
"The annoying thing is, our school decile rates are bound to go up yet half the people who move here are double-income types with no children. They soon sell their houses on for a profit and leave."
Thomson has two boys at decile-6 Birkenhead College. Her youngest lad attends Verran Primary School, presently rated decile 7.
Every Christmas she has to find about $1,500 to pay for school donations, uniforms and stationary, plus extra activities like music and sport.
"The local schools are brilliant but because the area is a lot wealthier than it was in 2006, I am certain the decile ratings will go up," she says. "This will mean a real financial burden for long-term residents who now could not afford to even buy a house here."
Thomson, an accountant, says she will have to make sacrifices like pulling her boys out of sports or cutting back on music-related activities because they may no longer be affordable.
"I am very concerned that parents like myself are in for a real shock when the decile ratings are reviewed."
According to ministry figures, the funding difference between a typical 1,000-pupil decile 1 and decile 10 school can amount to more than $900,000 a year. The money is used to fund resources like support staff and equipment.
About 28 New Zealand schools applied for decile reviews in the past two years and were given lower ratings as a result. Another 23 applied but no change was granted or the applications were not completed.
Snells Beach School, north of Auckland, got its rating dropped from decile 8 to 7 this year, netting an additional $40,000 in funding.
"The likelihood is that decile numbers will go up significantly across Auckland when the new ratings are decided so everyone is sitting tight," says principal Jill Corkin. "I was not concerned about any perceived loss of status when our decile rating went down. These numbers are nothing to do with how good or bad a school is and it is sad a lot of parents think that way."
In Otahuhu, south Auckland, Frances Nelson is in charge of decile-2 Fairburn School. After the last census it was promoted from decile 1, leaving her with a $70,000 funding shortfall. She is worried the same will happen again next year. "I have 700 students to cater for and I am dreading the prospect of having our funding reduced," she says. "I am now starting to think through the implications of this happening because the last time we were given very short notice and it played havoc with the school and our resources. It would be a nightmare."
One big winner from a significant decile drop is tiny rural Te Poi School in Waikato. Last year, principal Linda Woolhouse got the rating chopped from decile 9 to 5.
The move was backed by every school parent and it brought in "thousands of dollars" in extra funding. As a result, the school roll has jumped from 25 to 46 because of greater resources.
"I used to work at a low-decile school in Hamilton and couldn't understand why Te Poi had been given such a high rating," Woolhouse says.
Britain's great wartime leader Sir Winston Churchill coined the phrase: "Democracy is the worst form of government, except for all those others that have been tried."
Something similar might be said about New Zealand's school decile system. It is not perfect but is perhaps still better than alternatives.
Decile was a new term here when it was introduced by the National Government in the mid 1990s, in response to the polarising of schooling caused by their previous dezoning policy. It was originally called Equity Funding.
The ministry says no changes are planned: "It is important to note, decile funding accounts for approximately 13 per cent of all operational funding. It therefore does not play a big role in determining the overall funding a school receives," a ministry spokeswoman says. "Decile-based funding provides additional money to schools in lower socio-economic communities to overcome barriers to learning."
Education experts have mixed views on its efficacy.
Ann Dunphy, lecturer in education at the University of Auckland, believes it simply promotes unwelcome competitive marketing between schools and confuses parents.
She says some schools go to great lengths to retain a decile 9 or 10 status because of the perceptions of success that go with it. "Even if securing a lower rating meant the school would receive more government funding, they are reluctant for this to happen in case it looks like standards are slipping.
"Many big schools in the Auckland area are already very well funded by taking in foreign students and I know some schools get more than $1m a year from that. They also receive large donations from parents and old boys and are keen to keep things that way."
Dunphy believes many low decile schools in poorer areas now have an undeserved bad reputation that is difficult to shake off.
"The decile ratings are useful in terms of measuring the wealth of a community, but principals at low decile schools want to get rid them because it is leaving their schools and students stigmatised."
John Minto, national chairman of the Quality Public Education Coalition, goes further.
He thinks it is time decile ratings were scrapped.
"The decile system is a very crude measurement tool and anyway, schools should not be able to seek donations from parents at all," he says. "All schools in the country should be fully funded. At one time, it didn't matter which school you went to in New Zealand because they were pretty much equal."
Educational sociologist Professor Martin Thrupp, from the University of Waikato, defends the system, arguing that it is inescapable that socio-economic issues affect school performance.
"Deciles often just confirm what parents already know about the social geography of their area," he explains. "The resulting funding props up and compensates the lower decile schools, which is really important and what it is meant to do.
"People who are unhappy that the decile rating of their local school will go up because the community has become wealthier, should remember that they are benefiting from things like their houses increasing in value and having improved facilities in their area.
"However," he acknowledges, "there is room for debate over whether the decile system is adding to residential segregation in some areas of Auckland."
Back in the Auckland neighbourhood of Oranga, Louise Trevella remains comfortable with her decision to send her kids to the nearest local school, for resisting using decile numbers as a "status" guide. Oranga School may or may not climb the decile rankings next year - but the Trevellas' decision will be made by visiting the school, checking out the classrooms and playground, meeting the principal, teachers and pupils.
"I went to a local school and mixed with kids from all kinds of backgrounds. It didn't do me any harm," she says. "I want my children to have a good education and learn tolerance and respect towards others, not be elitist.
"If I sent them to a higher decile school further away, I would probably also be required to do a lot more to raise cash for the school and pay higher donations because of less government funding."
She concludes: "I would rather just make the fudge for the school fair than have to supply the stall as well."
