Image caption Lisa Williams' son ordered Welsh-language revision guides months ago

Teachers are angry pupils have been waiting months for some Welsh-language GCSE revision guides.

They say Welsh-medium school pupils have lost out because the higher maths and business studies guides have only been available in English, and exams get under way this week.

The exam board WJEC said it had no control over publishers' stock levels.

It said the business studies revision guide had now been sent to schools, but higher maths was still not available.

Teacher Lisa Williams, whose own son is still waiting for revision guides ordered months ago, said it was now too late.

"The exams are about to start. It's May. Why weren't these booklets available three months, six months ago? These children are about to sit their exams. It's not acceptable," she said.

Ms Williams, who works at Ysgol Gyfun Cwm Rhymni in Caerphilly county, added: "I don't know who is to blame. Is it WJEC? Is it the publishers? This problem needs to be solved before more pupils are disadvantaged."

Image caption Maths teacher Hafina Ault said the revision guides were available much later than the English-language materials

Hafina Ault, the head of the maths department at the school, said the situation was unfair.

"Any resources that are published, they are always in English first and we are always waiting for months," she said.

"It undermines the language and the language's importance."

Plaid Cymru's education spokeswoman Sian Gwenllian AM said she was worried it would mean some pupils would not reach their full potential, and that the Welsh Government lacked the will to tackle the problem.

The Welsh Government said it was working to ensure revision materials in both languages were produced at the same time in future.

WJEC also said it was continuing to work with publishers to reduce any delays in publishing textbooks.

There have been similar problems previously - when a new maths GCSE course was launched in autumn 2015, the Welsh-medium textbooks were not available until the following May.