A key pledge by Labour to increase school spending may fail to close the per-pupil funding gap with England, it has emerged.
During his campaign to become Labour leader in 2009, Carwyn Jones promised that the Assembly government would spend 1 per cent more on education than the block grant it receives from Westminster every year.
Mr Jones said the aim was to reach "parity" with pupil funding in England - figures in January revealed that England now spends pound;604 more per pupil than Wales.
The Labour manifesto for the forthcoming Assembly elections has retained the 1 per cent pledge, but has dropped mention of matching spending in England.
A Labour party spokesman has told TES Cymru that schools will see annual funding increases only on the assumption that the block grant from Westminster is not cut.
This year the Assembly government protected school spending, despite a cut of pound;500 million in the block grant from Westminster. The Assembly has also indicated that it will hold spending steady for the next two years.
But concerns have been raised that if the grant suffers as further pressure is put on public spending, the gap between Welsh and English pupils will not be reduced.
NAHT Cymru director Anna Brychan said it was understood from Mr Jones' manifesto pledge that he would seek to close the funding gap.
"School leaders would find it hard to accept any rowing back on an apparently clear promise," she said.
Dr Philip Dixon, director of ATL Cymru, said that the "clear impression" had been given that the funding gap would close and that teachers would feel "very aggrieved" if it did not. NASUWT Wales organiser Rex Phillips said the union would hold Mr Jones to his pledge.
David Reynolds, education professor at Southampton University and a senior policy adviser to the Assembly government, said closing the gap may depend on the development of free schools and academies across the border.
"It's not clear the extent to which we will be getting parity with England until it is clear what England is doing with its educational funding," he said.
Education funding has become a key battleground in the Assembly election campaign, with Plaid Cymru pledging to introduce funding based on catchment areas.
The Conservatives would fund schools directly to save pound;102 million a year and cut out local bureaucracy, while the Liberal Democrats say they would introduce a pupil premium.
A Labour party spokesman said: "We are committed to spending more on education; that's why we'll raise schools funding by 1 per cent above the percentage change in the block grant from the UK Government.
"Assuming the Conservative-led UK Government doesn't cut our grant, this should mean additional increases for Welsh schools."