I agree with Andreas Schleicher’s rejection of academic criticisms that the Programme for International Student Assessment is fundamentally flawed (“Attacks on Pisa are entirely unjustified”, Comment, 2 August). No assessment is perfect but Pisa’s methodology is thoroughly interrogated and about as rigorous as it can be. It is also worth remembering that, with its focus on the use and application of knowledge and equity of achievement, Pisa provides powerful evidence for those of us who believe in inclusive and comprehensive education systems.

What is frustrating about these criticisms is that they are a diversion from key questions about Pisa outcomes. Are the results from the three “literacies” a sufficient proxy for a 360-degree evaluation of a country’s education system? Given that the body behind Pisa, the Organisation for Economic Cooperation and Development (OECD), has acknowledged that uncertainty is part of the Pisa outcomes, should this not form a high-profile caveat in the reports? Shouldn’t the OECD be more robust in rejecting outrageous ministerial claims for Pisa evidence?

The worst mistake would be to shoot the Pisa messenger instead of using its evidence to create powerful arguments against those who propose the dismantling of public education.

John Bangs, Chair of the OECD Trade Union Advisory Committee’s working group on education.