By Colette Hume Education correspondent, BBC Wales

Ring-fencing education may be the only way forward, says the NAHT

The National Association of Head Teachers (NAHT) said its research shows spending by 14 of the 22 councils is below expected budget levels.

It says those local authorities spending below these levels should be compelled to give an explanation.

But the Welsh Local Government Association said local councils have increased their budgets.

The NAHT examined the Indicator-Based Assessment (IBA) which is a budget relating to the delivery of education services.

Although councils are free to spend above or below the level of their IBA, the union says those 14 authorities spending below should be compelled by the Welsh Assembly Government to explain themselves.

COUNCIL BY COUNCIL, A-G: Anglesey - 95.2% Blaenau Gwent - 99.9% Bridgend - 99.1% Caerphilly - 100.2% Cardiff - 100.5% Carmarthenshire - 102.2% Ceredigion - 98% Conwy - 101.1% Denbighshire - 98.3% Flintshire - 97.4% Gwynedd - 96.1% Education net revenue as a % of the IBA. Source: NAHT

Iwan Guy, NAHT Cymru school funding consultant, said: "Many authorities simply aren't spending as much on education as they say they will.

"Unless the Welsh Assembly Government is prepared to take a more proactive role in monitoring the expenditure and to take action when authorities spend below the IBA, we feel that the only way forward to secure school funding would be to ring-fence spending on education."

But that could be an unpopular move.

Councils in Wales have enjoyed fiscal freedom and many would reject any moves to dictate how budgets were spent.

However, many teachers say they would welcome a ring-fenced education pot.

Unions have long complained about what they have described as a "funding fog" and a lack of transparency.

COUNCIL BY COUNCIL, M-W: Merthyr Tydfil - 98.3% Monmouthshire - 94.3% Neath - 100.2% Newport - 97.7% Pembrokeshire - 99.5% Powys - 98.3% Rhondda Cynon Taff - 101.7% Swansea - 100.9% Torfaen - 98.2% Vale of Glamorgan - 98.9% Wrexham - 100.7% Education net revenue as a % of the IBA. Source: NAHT

But the Welsh Local Government Association (WLGA) said authorities were entitled to spend budgets according to their own priorities, adding that education budgets had actually increased.

John Davies, spokesman for lifelong learning, said: "Compared to last year, local authorities have also increased their education budgets by 3.8% on average.

"While this is not as high as the overall increase this is to be expected since pupil numbers are falling while demand for other services, e.g. social services client numbers, are increasing.

"However, local authority spend per pupil has increased by 7.4% during the same period."

Capital investment in school buildings was recognised by local authorities as one of the top priorities, he added.

'Demand answers'

Among the authorities the NAHT says are not spending enough is Denbighshire.

Last Friday, it received a damning report from the education watchdog Estyn.

The 35-page report accused the authority of poor leadership at every level and slammed the authority's falling exam results.

On that day, Education Minister Jane Hutt wrote to the council's leader Rhiannon Hughes and told her it was clear the standard of performance of Denbighshire's education service was not acceptable.

Anna Brychan, director of NAHT Cymru, said: "Our members will be very concerned about the picture revealed by these figures. We hope they will take them to their local school budget forums and demand answers."

A Welsh Assembly Government spokesperson said it was local authorities which set budgets for schools and other local services out of funding provided in the local government settlement.

They are "accountable" for those decisions, said the spokesperson, adding: "Local authorities are responsible for spending their allocations year on year.

"The assembly government has no powers to impose sanctions on a local authority for not spending to its education IBA or any other level."