When experiments are run in public policy, evidence can be collected and the policies can be reviewed, scored and either rolled out, tweaked or abandoned. Not every area of policy lends itself to evidence-based analysis, but sometimes it’s clear-cut. We can see, for example, whether tax revenues rise or fall in response to fiscal reforms. Politicians are generally enthusiastic about evidence-based policy, and this is particularly true in Scotland where official documents, consultations and reports invariably state that “evidence and analysis are at the heart of policy making in the Scottish Government.”

What, therefore, will Scottish government ministers make of the latest findings from the highly respected Programme for International Student Assessment (PISA), released yesterday? The findings are clear, and damning. Since the Scottish National Party introduced its Curriculum for Excellence in 2010, Scottish pupils have declined – disastrously – in maths, reading and science. The SNP’s approach to education was to replace what they saw as a “narrow focus on knowledge” with a more rounded approach that emphasised “relevance” and “skills for life.” Teachers’ judgment came to count for more than formal examinations. This was, we were told, a radical and progressive approach to education.

The Welsh government followed the same path, focusing on “holistic student development” designed to produce “ethical, informed citizens.” Welsh students have also continued their downward slump when it comes to such outdated concepts as reading and adding up.

Labour risks copying the mistakes of Scotland and Wales

England, on the other hand, has performed remarkably well, for which we should thank Michael Gove who, as education secretary, dismissed the fashionable approach of our Celtic cousins in favour of a structured, knowledge-rich curriculum. English pupils’ sustained progress in maths, reading and science has moved the country into the top ten internationally.

Lindsay Paterson, Professor Emeritus of Education Policy at the University of Edinburgh, looked at yesterday’s PISA rankings and concluded “the policy lessons are obvious.” Indeed they are. And yet, alarmingly, Labour wants to move away from the demonstrably successful approach taken in English schools since 2010 and towards the kind of “broader curriculum, fewer exams” model tried in Wales and Scotland. Perhaps the Education Secretary thinks she can run the same experiment as Scotland and Wales and produce a different result.

Any attempt to do so risks inflicting the same disaster on pupils in England that has been playing out in parts of the UK that have ignored evidence for years.