Last week, the sporadic debate about curriculum narrowing under Curriculum for Excellence - a discussion that seems to emerge every year or so - blew up again in the Scottish Parliament.

This time, the issue was subject to scrutiny by the Education and Skills Committee and subsequently led to a clash of party leaders in the chamber. According to Ruth Davidson, the Conservative leader, “we have seen attainment in National exams down by a third compared to the old Standard Grades”.

First Minister Nicola Sturgeon responded by stating: “When we look at National 5 level, the proportion leaving school with an award has risen nine percentage points: it was 77.1 per cent in 2009-10, it was 86.1 per cent in 2016-17, and at Higher level the gap between the richest and the poorest has fallen by almost seven percentage points.”

According to these arguments, attainment at National 5 has both fallen and risen simultaneously - something that is clearly impossible. This paradoxical situation is symptomatic of public debate on a topic which has genuine implications for education, but which is not understood by many of the players presenting arguments and counter-arguments.

Many of these arguments are based upon a superficial analysis of publicly available data on examination results, which does not fully capture this complex and nuanced situation. Moreover, the situation has been exacerbated by the misleading presentation of enrolment as attainment. So what exactly is happening?

What the data says

First, analysis of available data from 2012-17 (Scottish Qualifications Authority data, school leavers data, etc) illustrates clearly that attainment is rising. More young people are leaving school with higher levels of qualifications and, moreover, this effect is especially marked for students from socially disadvantaged backgrounds. So it is inaccurate to claim that attainment has fallen.

Second, it is clear that the curriculum in the senior phase - notably in S4, as students undertake N3/4/5 qualifications - is narrowing. Prior to the introduction of the new CfE qualifications, it was usual for students to take eight qualifications at this stage of education. Six options is much more usual now, and in some cases as few as five, meaning that there has been a significant reduction in the number of subjects studied in S4.

Our recent analysis of school-level data relating to qualifications suggests that this effect is especially marked for students in schools serving low-socioeconomic-status (SES) areas. In other words, provision of education in the senior phase seems to be socially stratified: if you attend school in a wealthy area, you are more likely to be able to study seven or eight subjects at N5, whereas if you attend school in a relatively disadvantaged area, the number of subjects studied is likely to be fewer. We do not yet know why this is occurring - more research is needed - but we do know from the data that it is happening

There are several more points that need to be made about this curriculum-narrowing. First, I wish to reiterate that this is not a drop in attainment, as has been claimed by some. It is a fall in the number of qualifications taken. It is misleading to describe a drop in enrolment as a drop in attainment, as has been the case in much recent political debate and media coverage.

That is not to say that a drop in enrolment is not a significant issue. There is evidence, for example, that reduced choice in S4 has disproportionally affected the uptake of modern languages (although this is a long-term trend that preceded the introduction of new qualifications in 2014), and, to a lesser extent, arts subjects. Presumably this is because students will choose subjects deemed to be more important (English, Stem subjects), and it is likely that there will be effects on subsequent uptake of these subjects at Higher and beyond. Again, we do not have a clear picture of these effects, and more research is needed.

Instrumental view of education

This phenomenon raises some troubling questions. I accept that the balance between breadth and attainment is contested terrain. It is likely that narrowing choice, particularly for low-SES student populations who have traditionally struggled to attain good qualifications, is a factor behind the raised attainment previously noted. One might argue that we are serving these students well, if we enable them to attain grades that get them into positive destinations, including further and higher education, and that a loss of breadth is an acceptable compromise. But this is to take an instrumental view of education as merely a route in qualifications and positive destinations.

There is a further question about whether we are selling these young people short if we send them into a complex and turbulent world (characterised, for instance, by Brexit, climate change, social upheaval, etc) without an adequately broad education that affords them knowledge of that world. The social stratification in current trends is particularly troubling.

Another issue worth mentioning, as raised in England by head of Ofsted Amanda Spielman last week, is the question of whether decisions about curriculum provision are being made in the interests of students themselves or for the benefit of schools. Put bluntly, are decisions to raise attainment through narrowing the curriculum about providing young people with better qualifications, or are they more about raising attainment to boost the image of the school within a highly performative education system?

From this discussion, two issues arise for me. The first is that we need more research on this issue, both to identify patterns and to understand them. This will prevent the sort of misleading claims that have been made in recent weeks. Second, we need a more mature public debate than that seen recently - one that explores the fundamental question “what are schools for?” and one that seeks to pin down what sort of schooling we really want in Scotland.

Mark Priestley is a professor of education at the University of Stirling and director of the Stirling Network for Curriculum Studies. This piece was originally published on his blog

For further detail on the analysis that informs this piece, see annexe C (p42) of the papers of the 19 September 2018 meeting of the Scottish Parliament’s Education and Skills Committee