Those of you who remember your school days and those who currently have kids at school, may be aware of streaming – the practice of separating students into classes based on their stage of learning.  

Streaming is common in secondary schools. According to the OECD 2018, 83.5% of New Zealand secondary schools streamed some or all subjects. The rate of streaming for mathematics was 95%.

Proponents of streaming argue that grouping students at similar stages of learning allows for more targeted instruction. However, several New Zealand-based organisations and academics argue that streaming widens learning gaps between advantaged and disadvantaged students. These commentators say that streaming negatively affects Māori and Pasifika students in particular.  

The New Zealand Initiative’s newest report, Class Divides: The impact of streaming on educational achievement and equality, takes a deep dive into the evidence. The central finding is that there simply is not enough research in the New Zealand context. There is plenty of small-scale, mostly qualitative research.

However, no large-scale studies have measured the impact of New Zealand’s streaming practices on learning. We don’t even know which schools stream (though we know, from OECD data, that most of them do). Neither do we know how schools that stream go about it, how teaching and curriculum tend to differ between streams, or how it affects learning. 

We filed an Official Information Act request with the Ministry of Education to answer these questions. The ministry said it does not collect data on streaming and does not monitor streaming practices.  

We first must have the answers to these questions before contemplating policy changes like banning streaming. One thing the large body of international research suggests is that the effects of streaming on learning depend on factors like the teaching and curriculum in lower streams.  

We cannot, therefore, draw reliable conclusions from international research about streaming in New Zealand without at least knowing more about how the New Zealand schools typically go about it. Our report recommends that the ministry commissions a large-scale quantitative study to measure the prevalence, methods and impact of streaming in New Zealand schools.  

International research has identified risks associated with streaming. It is often associated with wider learning gaps between advantaged and disadvantaged students than are typical in schools that do not stream. This does not prove that streaming causes those wider gaps – association alone does not establish causation. We should, however, take seriously the possibility that it might. 

One way in which streaming might be harmful to the learning of Māori and Pasifika students is through a phenomenon known as stereotype threat. In the educational context, stereotype threat occurs when students from groups stereotyped as poor learners – as, unfortunately, Māori and Pasifika often are – are exposed to situations that remind them of those stereotypes.

This can cause some students to perform less well than they otherwise would by damaging their self-confidence. Being placed in a low stream seems likely to act as a reminder. 

On the other hand, proponents can draw evidence from the science of learning to support their claim that sorting students into classes at similar stages of learning can benefit students in all streams, in some subjects at least.

For example, in mathematics, which is probably the most commonly streamed subject, each learning step must be thoroughly learned before building on it with further learning. If not, students will likely experience cognitive overload, resulting in confusion and frustration. If that state persists, it becomes demotivating. 

If a class comprises students at very different stages of learning, it is difficult for a teacher to move at a pace that suits all students. Those who are further ahead are likely to be bored, and those who struggle are likely to experience cognitive overload if the pace is too fast for them.  

Destreaming – the cessation of streaming in a school – also has risks. Research from the United States describes cases of schools, or entire school districts, destreaming - only to see educational inequality, as well as overall results, get worse.

There are also examples of destreaming being associated with a reduction of inequality and better overall outcomes. A critical factor for successful destreaming seems to be providing additional teaching support for students previously in lower streams. That, of course, entails additional resources. 

The debate around streaming has been going for over a century and is unlikely to end anytime soon. In publishing the Class Divides report, we do not seek to end the debate. Instead, we hope to demonstrate that the issue is nuanced and complex. Before the conversation about streaming in New Zealand can move on, we need to know more about how it is implemented in our schools and how it affects the learning of students in different streams.

We look forward to seeing the ministry leading its own research on this issue to allow schools to make informed decisions.