Teachers are united in their opposition to a proposed "earth- shattering" Wales-only law making the 14-19 learning pathways, a vocationally led curriculum, compulsory in just under a year.
Estyn, the Welsh inspectorate, is opposed to the Assembly government's plans and has warned a common funding system for schools and colleges must be in place first.
There was an outcry in the teaching profession this week after the realisation that the learning and skills measure will make the curriculum a statutory requirement one year earlier than its original 2010 deadline.
Heads and unions are calling for a three-year delay, believing premature enforcement will lead to another fiasco similar to that of the foundation phase. The statutory introduction of the play-led curriculum for all reception pupils, intended to be a legal requirement last month, was delayed for one year after officials admitted they had got their sums wrong and it was under-funded.
At present, the 14-19 pathways is voluntary, and provides teenagers with a wider choice of academic and vocational courses at schools and colleges, compulsory work experience and the support of a one-to-one learning coach.
Schools have been phasing in parts of the curriculum since 2005 following publication of the Chapman report and the aim of ensuring 95 per cent of Wales's 25-year-olds are in education, employment or training by 2015. Teachers and unions have supported the strategy in principle from the outset, but have always had funding concerns. The present per-pupil funding system means schools and colleges compete for students, making collaboration difficult.
United in their condemnation of the move, which they say has been sprung on them without consultation, representatives from every teacher union told an Assembly committee last week that the measure, drawn up in July, should be voted out of the Senedd.
Dr Phil Dixon, director of the Association of Teachers and Lecturers Cymru, said: "It's far too ambitious to think we can go forward in 2009. Schools and colleges are chronically under-funded."
Heads told TES Cymru this week that the planned legislation could not come at a worse time, with schools facing tighter budgets and a raft of new policies.
Blackwood Comprehensive, near Caerphilly, has strong links with Coleg Gwent, but head Mike Pickard said: "To be able to go to the extent this measure requires in such a short time is not feasible."
Phil Whitcombe, president of ASCL and head of Bryn Hafren Comprehensive in Barry, questioned the need for the legally binding measure. "This is potentially the most earth-shattering thing to hit the secondary sector for many years," he said. "I think we are pushing too hard too fast."
But John Griffiths, deputy minister for skills, said the timetable was realistic, achievable and based on the progress made so far.