Serious concerns about reforms of the curriculum for 14 to 19-year-olds, and their impact on Welsh-medium education, will be raised at next week's Eisteddfod in Swansea.
Teaching union UCAC says it is worried about the viability of the Assembly government's promises to provide wider learning opportunities for all teenagers, and says issues over funding, partnerships between providers and teacher workload need to be urgently addressed if the plan is to work.
The government's Learning Pathways 14-19 programme aims to transform learning provision for all young people in Wales. It proposes a more flexible and balanced approach to the education of 14 to 19-year-olds, providing a wider range of vocational, work-based and academic experiences.
The aim is to reduce the high proportion of disaffected young people who drop out of school with few or no qualifications. Even bolder, it wants 95 per cent of young people by the age of 25 to be ready for high-skilled employment or higher education by 2015.
Elaine Edwards, UCAC's policy officer, said the principle of attempting to close the gap between the disaffected and the motivated was a noble one, but believes that unsolved problems still remain.
"The Assembly needs to be realistic about funding," she said. "Falling rolls will mean less money, but if we want to increase opportunities then that is going to be more costly.
"UCAC has concerns about health and work-life balance issues arising from putting the policy into practice, such as additional training, working extended hours and pressure to develop new courses or to diversify."
Aeron Rees, a 14-19 network co-ordinator in Ceredigion but soon to take over as headteacher at the county's Ysgol Gyfun Dyffryn Teifi, said the principle of widening access was a "laudable" one, but described the funding mechanism as "complex, burdensome and bureaucratic".
"The 14-19 vision is geared towards more choice for young people, but as options proliferate there will be added pressure on traditional subjects and this will make the curriculum more costly to run," said Mr Rees.
He will raise concerns at UCAC's public meeting on Tuesday about the possible demise of traditional subjects, as well as the implications for Welsh-medium education, which could suffer from a lack of resources.
Peter Griffiths, head of Ysgol Gyfun Rhydfelen in Pontypridd, said that Welsh-medium schools in particular will need to be innovative in their approach to widening the curriculum to ensure that Welsh-language skills are not neglected in the process.
Partnership working is a key element of the 14-19 policy and will involve schools, colleges, training providers, community groups and the voluntary and business sector working together.
But Wendy Edwards, manager of the new lifelong learning centre at Garth Olwg, which is linked to Ysgol Gyfun Rhydfelen, said: "To develop true partnerships there must be co-operation, and each partner must be ready to potentially give up part of their own agenda for the learner. This is unlikely to happen unless the funding mechanism is changed."
An Assembly government spokesman said it prided itself on working in partnership with others on 14-19, and had set aside pound;41 million for Learning Pathways.
He added: "This, plus the significant amount of funding already available for 14-19 year olds in schools, colleges and work-based training, will enable most learners to experience most key elements."
UCAC's public meeting on 14-19 takes place at the Eisteddfod on Tuesday in the societies' tent, between 12pm and 1.30pm