The inequalities of streaming
Imagine that your boss gives you an intelligence test on your first day of work. The organisation groups you in a team based on your ability, as measured by the test.
The tall poppies are grouped together on the top floor and are pumped with extra resources - great managers, coaching and development, and more opportunities.
The weakest leftovers are cobbled together on the bottom floor where the less competent managers also are relegated: the cabbage floor. The floors in between represent the different layers of ability.
It's a ridiculous scenario. Employers know it is much more effective to group people of mixed capability together, so that the highest performers lead the way for others.
No doubt more capable people and higher performers are paid better and provided with more opportunities in the workforce, but an employer wouldn't dream of streaming people by ability.
But schools do.
An untold story from the recent and much-anticipated 2012 cycle of the Programme for International Student Assessment (Pisa) study is that virtually all New Zealand secondary schools use ability grouping.
For mathematics, 60 per cent of schools use between-class ability grouping (known as streaming or tracking) for all classes, 38 per cent stream some classes, and 1 per cent don't stream.
Professor Garry Hornby at the University of Canterbury found that out of 15 secondary schools in Christchurch, all but one streamed kids by ability, as did seven out of nine intermediate schools.
The latest Pisa findings confirm his research on a national level.
Looking at the Pisa results in an international context reveals the most fascinating part of the story: New Zealand is number one in the OECD (Organisation for Economic Co-operation and Development) for streaming students within schools by ability.
Stanford University researcher Eric Hanushek, a world leader in economic analysis of educational issues, in summary of his research on streaming policies, has commented that "countries lose out in terms of distribution of outcomes, and possibly also in levels of outcomes, by pursuing such [streaming] policies".
The research shows that kids with lower ability do better when they are grouped with higher achievers, and higher achievers do just as well.
So what have other countries learned about the way they stream their students?
This year on a research trip I travelled to Germany, a country that received a "Pisa shock" of its own in 2000 when the OECD first began assessing 15-year-olds around the world.
Since its Pisa shock Germany has improved performance and narrowed the gap.
At the same time, New Zealand saw worse performance and a widening of the gap. At the time I travelled there, New Zealand was ahead of Germany in international rankings.
The 2012 Pisa findings released two weeks ago reveal that New Zealand is now lagging well behind.
Prior to 2000, Germany had what has been described as a 'feudal class system' of education where students were streamed into three different types of secondary school: an upper stream that would lead to university study, a middle stream that would lead to white-collar middle management careers, and a blue-collar lower stream.
Andreas Schleicher, head of the Pisa programme and dubbed the world's school master, poignantly summed up Germany's streaming system: Children were "divided between those deemed to pursue the careers of knowledge workers and those who would end up working for the knowledge workers, mainly along socio-economic lines".
Since 2000, many states in Germany have done away from the bottom stream that was considered a 'dumping ground' for immigrant and lower-class children, merging them into one vocational stream.
It is difficult to know whether the narrowing of the gap among German students is due to changes in streaming as this time period also corresponded with socio-demographic shifts: the poor kids in 2012 were richer than the poor kids of 2000.
Nevertheless, it is plausible that doing away with the stigmatised cabbage schools has played a part in greater equity for German students.
New Zealand doesn't separate kids into different schools by ability, but it certainly does within schools.
Quoted in a Stuff article on streaming in May, Porirua's Bishop Viard College principal Teresa Cargo remarked: "Students are pretty quick to start labelling one another and themselves. Kids will say the 'cabbage class'."
Students in New Zealand are all too aware of where they fit in the social structure of school, whether they are the brainy nerdy kids or the cabbages.
It also begs the question of whether top teachers are being deployed to the top classes.
New Zealand has wide gaps in educational performance and is one of the worst countries for correcting for social disadvantage.
And unusually, New Zealand has greater variation in student achievement within schools than between schools.
Researchers puzzle over this, but the propensity towards within-school streaming seems to offer some clues.
Perhaps it's time for New Zealand secondary schools to take a lesson from the workplace, and reconsider their streaming policies.
Rose Patterson is a research fellow at the New Zealand Initiative.