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Last year Welsh 15-year-olds joined half a million pupils from across the world in sitting a series of tests designed to measure their expertise in science, maths and reading. 

After 12 months of number crunching, the results of those tests – known as PISA – will be published on Tuesday. 

With them will come a mass of figures and tables allowing us to compare the performance of Welsh students against their peers from around the globe. 

Ahead of that publication, Nelli Bird and a panel of experts look back at Wales’ previous PISA performances and how they’ve shaped Welsh education policy.

And they look forward to Tuesday’s results and the challenges they may throw up for Welsh pupils, teachers and politicians.