The new foundation phase for three to seven-year-olds has been hailed as a new era in early-years education, but there are growing concerns about its financial sustainability, with some pilot schools still waiting for funds.
Most of the 41 pilot schools and playgroups across Wales introduced the new play-based learning curriculum last month.
But TES Cymru found that some are still recruiting the extra staff needed for the prescribed 8:1 pupil-teacher ratio. Others are waiting for money from the Welsh Assembly.
An Assembly spokesman said grant offers were sent to all 22 local education authorities last month. But delays in processing funds have added to concerns that there may not be enough funding to sustain the hundreds of extra staff, new buildings and equipment needed when all early-years facilities are on board in 2008.
Teaching unions are calling for a detailed breakdown of how much money is available for the foundation phase.
Moelwen Gwyndaf, general secretary of UCAC, the Welsh-speaking teachers'
union, said: "Any new initiative has to be properly planned and resourced, or children are going to be let down.
"We want to see more transparency in how money will be allocated for the long term."
Early-years education receives pound;25 million a year from the Assembly.
Following last week's budget, there will be an extra pound;67m investment over the next three years, but the precise allocation for the foundation phase is not yet known.
Janet Ryder, Plaid Cymru education spokesperson, said the uncertainty is "symbolic of what is wrong with the way we fund our schools. Even if the foundation phase gets an extra pound;20m a year, that still only amounts to pound;1m per local authority, and I don't know how far that will stretch," she said.
Anna Brychan, director of the National Association of Head Teachers in Wales, said heads welcomed the foundation phase in principle but were worried that the resources may not be there to deliver in the longer term.
She said: "We think every school should be looked at in terms of staffing, space and facilities, and there needs to be dedicated funding so that every school can offer the same thing."
Children's personal development is at the heart of the foundation phase, where learning takes place through indoor and outdoor play-based activity.
It will amalgamate the current early-years and key stage 1 phases of the national curriculum.
St Mary's Church in Wales school, in Brynmawr, Blaenau Gwent, is one of the 41 pilot centres. It now has four members of staff, instead of two, to supervise the 28-strong nursery. And there are four members of staff for the 30 pupils in the reception class.
Staff are delighted with the results so far. Teacher Claire Wright, who now receives support from three nursery nurses, said it was rewarding to spend more time with individual children.
"Before, it was difficult to do more than one activity, but now we can have four small groups," she said. "We can structure the learning according to ability and it's easier to track pupil progress."
Ian Forbes, St Mary's head, agrees the change has been remarkable. "There are now too many teachers to fit into the staffroom," he said.
He described the initiative as an exciting time in education for the early years and said he hoped the funding would continue beyond two terms.
But the Welsh Assembly government insists that the foundation phase will not suffer from a lack of long-term funding.
A spokesman said: "The 41 pilot settings across Wales will be closely monitored and evaluated. As a result, we will be able to firm up detailed costings.
"It would be our intention, in the light of the outcomes of this evaluation, to roll out the foundation phase by September 2008."