Pupils who speak Welsh as a first language are gaining an unfair advantage in their GCSEs, by sitting exams intended for English speakers, according to a Welsh pressure group.
There are two forms of Welsh-language exam: one is intended for fluent speakers whose first language is Welsh, or who have attended a Welsh-medium school; the other is for pupils who have learned the language from scratch in the classroom.
But this two-tier system, says RhAG, the association of parents for Welsh-medium education, is currently being abused by pupils from Welsh-speaking backgrounds, who are choosing to sit exams designed to test second-language speakers.
The association said fluent candidates raised grade boundaries, penalising those for whom the GCSE was really intended.
"Welsh speakers are getting all the best marks," said Tim Pearce, spokesman for RhAG. "Because of the way the exam and marking system works, this means the others cannot do as well."
And it is not only Welsh second-language learners who suffer, says RhAG: first-language speakers are being disadvantaged as they are not being challenged. "They are not taxed as much by the courses as they should be, so they lose linguistic skills," said Mr Pearce.
Yet heads argue that there is clear justification for entering their pupils for the easier exam.
Neil Foden, head of the bilingual Ysgol Friars, in Bangor, allows his pupils to sit the second-language exam at the end of Year 9 or 10. The more able students then go on to sit the first-language exam.
"If they sit Welsh as a second language, they have a bankable qualification, and they can then go on and push themselves," he said.
"I could put a kid in for Welsh first-language who is expecting a row of As, and a C or D in Welsh language but it would demotivate them. We shouldn't turn them off the language."
A spokesperson for Jane Davidson, Welsh Assembly minister for education and lifelong learning, acknowledged that the issue of Welsh speakers doing the easier GCSE had been brought to her attention.
"We will be looking at it as part of a broader review of the 14 to 19 phase," she said.