Startling admissions, including claims that conditions in many of Wales's schools lag 50 years behind those in England, have been made on a show that investigated research commissioned by TES Cymru.
BBC Wales's current affairs show Week In Week Out explored the controversial findings that were unearthed by David Reynolds, professor of education at Plymouth University, for this paper last year.
In the course of his research, the academic found that each pupil in Wales had pound;500 less spent on them than their counterparts in England.
He also learnt that since 2003 the government had spent 6 per cent less than the UK average on education, but 7 per cent more on boosting Welsh culture, media and sport.
He concluded this had led to flagging standards. Since devolution, the number of pupils who gained top-grade GCSEs has fallen behind England by 7 per cent.
As anchor of the BBC show, Professor Reynolds spoke to many people with strong opinions about funding. Dr Mohammed Mehmet, chief executive of Denbighshire council who has been in Wales for the past 18 months, said many school buildings were in a dire state compared with those in England.
"Based on what I've seen, I have been struck by the difference - around 40 or 50 years in terms of what is visible and in the quality of the buildings," he said.
Professor Reynolds's research revealed that, between 2002 and 2008, recurrent and capital spending on education and training increased by 44 per cent in England, but by only 33 per cent in Wales - despite Wales's school buildings being in a worse state of repair.
Brian Lightman, head of St Cyres School in Penarth, told the show the pound;500 disparity in per-pupil funding was "probably the minimum", describing the regular power cuts, gas leaks and damp at his "perished" school building.
The Assembly government, which has never disputed Professor Reynolds' findings, refused to send someone to appear on the show, but released a statement saying that education had been one of Wales's success stories. It also said that substantial money had been made available and 12.5 per cent of its budget was spent on education.
The statement added: "It's not how much you spend, but how effectively you spend it."
But the show also called into question the school effectiveness framework, which is widely seen as the answer to funding issues because it focuses on teaching practice.
In its statement, the government said the sharing of best practice was improving. But Mike Gibbon, of Sandfields Comprehensive in Port Talbot, said he had not received many visits from colleagues in Wales, despite being head of one of the country's most successful school for exceeding GCSE expectations. Teachers from across the world visit his school to learn the secrets of its success, but he said only 20 per cent of them were from Wales.
When Professor Reynolds asked him why that might be, he suggested it could be a "cultural peculiarity", possibly stemming from defensiveness among Welsh heads.
The show produced mixed responses from education unions.
Anna Brychan, director of the heads' union NAHT Cymru, said: "With extra money, our members could do something significant for each of their pupils. But it's not necessarily the biggest spenders that get the best results.
Dr Philip Dixon, director of teachers' union ATL Cymru, said: "I think Professor Reynolds's findings are deeply disturbing. His points need to be listened to with respect by the Assembly government and not dismissed.
"I don't think throwing money at a problem solves it, but there comes a point where lack of spending has an effect. We are at that point."