Children are being cheated and standards are falling in Wales's schools because of significant underinvestment in education since devolution, research commissioned by TES Cymru reveals.
David Reynolds, professor of education at Plymouth University, says the Assembly government has underfunded schools, but there has been dramatically higher investment on nation building compared to the rest of the UK.
There has also been a widening funding gulf between England and Wales, and the percentage difference has hit 10 per cent - or Pounds 500 per pupil for an average 950-pupil secondary school. Since 2002-03, Professor Reynolds says there has been 6.4 per cent less spent on education compared to the rest of the UK taken as an average.
But he also found investment in general public services has shot up 8 per cent compared to the UK average and by 7.2 per cent for Welsh culture, media and sport, the English equivalent being recreation, culture and religion.
He says children's lives are being blighted and there is low teacher morale as a result.
"It is difficult to avoid a sense of shame looking at these figures because they mean young lives are being blighted and young potential is unrealised," says Professor Reynolds. "The Assembly government has played fast and loose with statistics in inappropriate ways in a democracy."
TES Cymru can also reveal the results of a snapshot survey of 100 headteachers.
When asked what they felt the biggest issue facing their school was, 63 per cent of the heads cited lack of funding.
The majority - 90 per cent - also strongly agreed that underfunding is having a negative impact on the standard of pupils' education in Wales.
According to Prof Reynolds, per pupil expenditure on education was higher in Wales than England in 1999, increasing 20.2 per cent in Wales and 16.7 per cent in England in the decade up to 2002-03.
However, although the amount of public expenditure on education has risen significantly, along with other UK countries, Wales has invested much less, and particularly compared to England.
Professor Reynolds blames the poor overall performance of 15-year-olds in the Programme for International Student Achievement (Pisa) results on underinvestment.
Wales was left trailing England, Scotland and Northern Ireland, in reading, maths and science tests in the results tables.
He also says Wales's local education authorities are holding back more money from schools, and the hold-back is now the highest in the world. He says 81 per cent was kept in 2007-08 compared to 76.1 per cent in 2002- 03.
In an interview with TES Cymru last month, David Hawker, Wales's newly appointed director of the department for children, education, lifelong learning and skills (Dcells) admitted there was less money in Welsh schools compared to England. The historic line has been for the Assembly government to deny any claims of underfunding. Better use of resources and improved teaching practice is seen as the way forward.
There are also many schools in Wales bucking the trend against their English neighbours and gaining better A*-C exam results, despite huge funding gaps.
Many heads in the TES Cymru poll are also supportive of education policies of the Assembly government since devolution; especially the introduction of the play-led foundation phase for under-7s and the abolishment of Sats and league tables.
A Welsh Assembly government spokesperson said: "David Reynolds seems content to run Wales down. He should stop looking over his shoulder to the rest of the UK and open his eyes to see the excellent work of schools, local authorities and government that is improving the lives of learners across Wales."
A Welsh Local Government Association spokesperson for education said: "For the past few years figures show that local authorities in Wales have consistently invested more money into education than they get from the Welsh Assembly government. While pupil spending may vary from authority to authority, this happens for a variety of reasons and local circumstances. Local authorities are best placed to decide where and how their money is spent and both the Wales Audit Office and the National Assembly's Funding Committee were very supportive of the way in which local authorities fund schools."