Almost half the teachers trained in Wales currently find work in English schools. Figures for 20001 show that out of 1,170 teachers who trained in Wales, 530 went to work in England - more than 45 per cent.
The employment migration was particularly marked in the primary sector, where 51 per cent of trainees found work in England and everyone who qualified to teach in special schools transferred there.
John Howson, recruitment expert and visiting professor at Oxford Brookes University, said: "There has been an expectation, in recent years, that some people who train in Wales will go and teach in England.
"If they're only going to be able to work in Wales, they will have to cut the number of training places, just to meet home demand."
His comments follow the introduction of a Welsh statutory induction year for newly qualified teachers. It is mandatory for those who gained qualified teacher status in Wales after April 1 this year.
The move marks another step towards autonomy. Since devolution in 1999, the Assembly has been working to forge an education system that is distinctly Welsh. There are no Welsh league tables, Welsh seven-year-olds do not sit written tests, and a new Welsh Baccalaureate qualification is being piloted this year.
Earlier this year, the General Teaching Council for Wales (GTCW) announced it would award qualified teaching status to all Welsh teaching graduates.
The award was previously presented on behalf of the Secretary of State for Education.
Teacher-training experts believe it may now become increasingly difficult for Welsh-trained teachers to cross the border into English schools.
Alun Charles, director of school-based studies at Trinity College, Carmarthen, said: "Training is in a Welsh, not an English context, which means you have a different ethos."
Gary Brace, GTCW chief executive, denies that teachers will find it difficult to transfer to England: "Although the system is diverging in terms of policy, the key thing is that we have mutual recognition of teaching qualifications.
"While priorities may shift, the standards remain the same: standards of conduct, standards of good practice and standards of competence."