A ministerial report on reforming the 14-19 curriculum - due out next month - will tackle the vexed question of how the reforms will be paid for.
The Assembly government wants teenagers to be offered a wider range of vocational and work-based courses, as well as traditional GCSEs and A-levels, in a bid to boost achievement, widen participation and reduce the numbers leaving school without any qualifications.
It has given pound;6 million to encourage collaboration between schools and colleges, and funding for 14-19 reforms will rise to pound;32.5m in 2007-8.
But heads at the National Association of Head Teachers Cymru's annual conference in the Vale of Glamorgan were today expected to call for a government review of the problems they face finding work-based pupil placements.
And delegates and speakers at a Welsh Secondary Schools Association (WSSA) conference in Cardiff, on 14-19 collaboration, also raised funding concerns.
Professor David Egan, the government's education adviser, told WSSA delegates: "We can't keep saying to FE, 'increase your activity but don't expect any increase in funding', any more than we can say that to schools."
He claimed that since 2001, spending on schools in Wales had increased around 40 per cent, on FE 30 per cent, and on higher education around 25 per cent.
"It's a remarkable increase but if we want more growth and inclusion we can't expect people to do that without discussion and funding," he added.
"The aspiration is not only to improve the quality of what we have (at 14-19) and to increase collaboration, it's also to say let's grow the involvement of young people in the system."
Professor Egan said next month's report, from deputy education minister Christine Chapman, would make a series of recommendations on how the 14-19 reforms can be taken forward.
Malcolm Charnley, principal of Coleg Glan Hafren, said the government was good on policy and vision, but less good at costing initiatives before launching them.
Also speaking at the WSSA conference, he said: "We have been encouraged to widen participation in education, and we are trying, but how do we achieve that in a capped-growth environment?"
The conference heard from heads and college leaders about collaborating to improve provision. Dr John Graystone, chief executive of fforwm, which represents Welsh colleges, told the delegates (mostly from schools): "What stops us collaborating is mistrust at the local level."
Funding, based on pupil numbers, does not encourage partnership either, he said. But while collaboration is hard work and far from glamorous, schools and colleges are responsible for ensuring equal provision for learners.
Greg Dixon, head of Connah's Quay high school, Deeside, said students there had benefited from a wider range of vocational courses, thanks to a 20-year-old consortium involving three other secondaries and the local FE college.
But the partners have had to build in rigid structures of meetings at different management levels, while joint timetabling and transporting pupils between sites are always problematic.
He added: "The understanding that we are all working for the common vision is vital. Should that be lost, the whole foundation can start to crumble."