As with too many others concerned to draw conclusions from international comparisons, Tim Oates confuses "the highest-performing jurisdictions" with "the best education systems in the world". Performance and quality are two very different concepts; the first is measurable, at least to some extent; the latter can only be judged, never quantified.
Who, then, is best qualified to judge educational "quality"? Not statisticians in government departments, nor politicians removed from school realities, nor self-proclaimed experts in assessment research and development.
In the final analysis, what counts is the experience and knowledge of the persons making the judgements. They do not come from leading international research projects, however "mammoth" in scale. Educational judgements of quality need to be made by current and former practitioners with shared, thoughtful, professionally validated experience in a wide variety of contexts, ideally international as well as national.
Colin Richards, Spark Bridge, Cumbria.