The quality of education in Britain’s schools will come under the microscope amid general election campaigning this week as the Organisation for Economic Cooperation and Development (OECD) publishes new international rankings of the performance of 15-year-olds in core subjects.

The timing of the OECD’s latest Programme for International Student Assessment (Pisa), which compares standardised test results in reading, maths and science across 79 countries, means any dramatic changes in the performances of pupils in England, Wales and Scotland is likely to become election fodder.

For the Conservatives in England, as well as the SNP in Scotland and Labour in Wales, the triennial Pisa results, published on Tuesday, form a report card on their time in office, with governments in London and Cardiff in particular seeking vindication for policy reforms.

“There’s a clear story that will come out if England goes up or down. But even if it stays stable there’s a story where people could say: ‘Well, Michael Gove made all those reforms that were meant to raise standards but nothing’s changed’,” said John Jerrim, a professor of social statistics at UCL’s Institute of Education.

“With the Conservatives having been in power for nine years, most of the children taking part will have spent most of their time at school under Conservative or coalition governments. High scores or low, there will be spin put on that.”

Jerrim warns that the Pisa results are likely to show few shifts in the underlying performances of British pupils, no matter where they are taught.

“The cross-country stuff is boring because nothing really changes,” Jerrim said, pointing to movements in Pisa rankings caused largely because of new entrants while the underlying scores for rich countries such as England have remained broadly stable.

“The differences between England and France or Germany on the Pisa scale is only 10 to 15 points usually, which is a really small difference. In terms of magnitude it’s not really anything to shout about.

“There’s a tendency for people to over-interpret what are actually quite small differences.”

Comparing the three sets of Pisa outcomes since 2009 shows remarkable consistency in the test scores of 15-year-olds in England. In the 2009 tests, England scored 493 in maths, followed by 495 in the 2012 edition, and 493 in 2015. The three years saw a similar pattern in reading (495, 500, 500) and science (515, 516, 512).

At the same time, the UK’s overall school performance has remained close to the OECD average.

Dr Sue Grey, a researcher at the Institute of Education in London, who studied the impact of Pisa on public perception and policymaking, said politicians would use its results to support their own agendas no matter what the outcomes.

Grey pointed to Gove’s use of Pisa’s data on school autonomy in successful countries to support his drive for free schools and academies, even though the OECD said schools in England already had more autonomy than those in east Asia being held up as models.

Similarly, a government push to adopt maths teaching methods from China was inspired by the Pisa success of schools in Shanghai. But the Department for Education’s own analysis found “no evidence” it had led to improvements in schools in England.

“People should bring a healthy degree of scepticism to any claims made by politicians of any party based on evidence from Pisa,” Grey said.

“Politicians will use the Pisa results to support whatever agenda they wish to pursue anyway, to hide the real issues they don’t want to speak about, and history suggests they won’t be challenged on any misuse or twisting of Pisa data in this way.”

Jerrim said there was also troubling questions about how the OECD arrives at its published scores for each country, using methodology he described as “a mysterious black box” that outsiders, including himself, had been unable to replicate.

“No one really knows how Pisa scores are created and the OECD really aren’t transparent about it,” Jerrim said.