Experts divided on results of Wales’ Pisa tests

Schools could choose to do the test in Welsh or English, and in 2025 pupils at 2,904 schools did it in English, 456 in Welsh, and 30 in a mix of both.

Prof John Jerrim, an academic at University College London, said over several rounds of Pisa, tests taken in Welsh had scored much lower.

But, this time, they had been about 70 marks lower in Welsh, with scores about 400 on average, he said.

The overall average was 459.

“More than likely… it’s a technical issue in and around the testing – so there’s something strange going on, quite possibly, in the translation,” he said.

“I don’t think we’ve quite got to the bottom of exactly what this is.”

But he thinks it is having an impact on the overall scores.

“That’s partly attributable to why Wales is doing so poorly, particularly in reading, and particularly compared to the other parts of the UK.

“I don’t think it can explain the entire difference.

“It’s artificially dragging the scores for Wales downwards, but it’s not the only thing at play here.”

Brychan said the government would be looking at the issue.

“I know that in the past there have been issues around translation of terms, for example, but a lot of work has happened to iron some of those out.

“If there are issues that we still need to deal with, we need to unpack those,” she said.

The Welsh government said it was working closely with the Organisation for Economic Co-operation and Development (OECD), which runs the tests, “to review the translation and linguistic adaptation arrangements for Pisa”.

“Welsh language and subject experts will continue to play an important role in validating assessment materials, supporting linguistic accuracy, cultural appropriateness and a fair basis for learners in Wales to demonstrate their knowledge and skills in future Pisa cycles,” it said.