Randomised controlled trials (RCTs) can be at risk of bias. Using data from a RCT, we considered the impact of post-randomisation bias. We compared the trial primary outcome, which was administered blindly, with the secondary outcome, which was not administered blindly. From 44 schools, 522 children were randomised to receive a one-to-one maths…

Reports of international large-scale assessments tend to evaluate and compare education system performance based on absolute scores. And policymakers refer to high-performing and economically prosperous education systems to enhance their own systemic features. But socioeconomic differences between systems compromise the plausibility of those…