When the Programme for International Students Assessment (PISA) started testing 15-year-olds in 2000, New Zealand students ranked second in reading and third in maths. Ever since, our scores have perpetually declined. Set starkly against this, pass rates for NCEA level 2, the national qualification typically completed by 16 and 17 year olds, have risen relentlessly.

So what is the story?

PISA assesses how well 15-year-old students have acquired knowledge and skills deemed essential for participation in society. By comparison, NCEA measures students of all abilities in all learning areas, allocating credits and grades for skills and knowledge. Depending on who you are, PISA and NCEA assess markedly different things.

Should we be worried about these differences? The answer to this is ‘yes’, if you care about social mobility.

Between 2002 and 2004, NCEA replaced the traditional trio of School Certificate, University Entrance and Bursary. With its equal emphasis on academic and vocational programmes, NCEA puts course choices from nuclear physics to nail technology into the hands of teachers, parents and students. Then in 2007 the new New Zealand Curriculum was introduced. A high-level document, it leaves much of the selection of curriculum content to its teachers.

Together, these changes mean that school boards and teachers choose what courses are taught, and what content is included.

This system works to the advantage of schools and students with aspirational, knowledgeable families; they encourage and support their children to take on challenging courses. But in school communities with less ambition and understanding, students’ fate is in the hands of their teachers. On top of this, league tables rank schools on their NCEA pass rates. This inevitably puts pressure on even the most virtuous of teachers, to encourage certain students into ‘safe’ courses. Such courses may neither challenge nor stretch these students.

Taken together, NCEA, the New Zealand Curriculum and our crude school accountability framework are a recipe for disaster. It is hard to imagine a system more likely to accentuate the gap between our ‘haves’ and our ‘have nots’.

Usefully, PISA also tells us something about the relative size of that gap. In their measure of the difference in performance between the top and bottom ten percent of a country’s students, New Zealand ranked 69th out of all the 71 countries who took part. Could there be a more damning indictment?

Could it be that it’s time for a change?