Since devolution in 1999, the number of Welsh-medium schools in urban, English-speaking areas has risen. But many rural schools in areas such as Powys and Carmarthenshire, traditionally Welsh-speaking, have struggled to recruit and many have had to advertise vacant posts repeatedly.
Wyn Williams, head of education for Carmarthenshire council, said: "There is a limited pool of Welsh-medium teachers anyway, so it's not easy. We've been having real trouble with job applications."
Helen Mary Jones, education spokeswoman for Plaid Cymru, said teachers were opting for a vibrant urban life. "In Cardiff, you can now have a very lively social life entirely through the medium of Welsh. So you need to do a lot to attract people to isolated areas." Ms Jones has called for financial incentives and sabbaticals for those who train to teach in Welsh.
Edwyn Williams, general secretary of UCAC, the Welsh speaking teachers' union, says the problem is compounded by an increase in alternative Welsh-speaking jobs created by devolution. There are now on average just twoapplicants for every Welsh-speaking teaching position, compared to six for each English-speaking post.
Sian Lloyd, the Welsh ITV weather forecaster, a promoter of the importance of Welsh-language education, said: "If you're a teacher in a small rural school, promotion is not a big prospect. Welsh-language speakers regard Cardiff as a Mecca. We've got to make rural areas more attractive, with better opportunities and more affordable housing."
A Welsh Assembly spokeswoman said there were plans to introduce financial incentives and sabbaticals for Welsh-medium teachers.