Figures obtained by TES Cymru under the Freedom of Information Act reveal the extent of GCSE underachievement at schools in deprived areas of Wales.
An analysis based on the free school meal (FSM) entitlement in both countries shows English schools outperform their equivalents in Wales by more than three times. The Assembly government acknowledged English schools do better and said it was doing all it could to raise standards.
But union officials said more money needed to be pumped into low-performing schools with "sustained extra resources" in line with England.
At Dylan Thomas community school in Swansea, the school with the highest number of FSMs in Wales at 62 per cent, just 14 per cent of pupils achieved five A*-C grade GCSE passes in 2004. However, an average of 42 per cent of pupils at 16 English schools, with 62 per cent of pupils or more eligible for FSMs, gained five good GCSE passes.
And at St Paul's Way community school in London, 59 per cent got five A*-C grade GCSE results, despite having the highest number of FSMs in England and Wales at 83 per cent.
Professor David Reynolds, an education adviser to the Westminster Government, said the figures showed England paid more attention to low-performing schools - because it had more of them. The academic, from Exeter university, said: "There have been some Welsh attempts to make improvements at the lowest schools but it is acknowledged that England has done more."
A sample of 15 Welsh schools with the highest FSMs from socially-deprived areas revealed that, on average, 29.5 per cent of pupils gained five or more A*-C grade GCSEs between 2002-4.
Four of these schools scored 25 per cent or less - the level at which some schools in England have faced threats of closure unless they improve.
Dylan Thomas school is earmarked for closure as part of local authority plans for reorganisation. The school did not wish to comment on its GCSE results. English schools have received support through the education action zones and Excellence in Cities initiatives, which focus on leadership and attendance.
A recent study, run with the Welsh Local Government Association, highlighted Welsh schools in deprived areas which were "bucking the trend".
But Brian Rowlands, secretary of the Secondary Heads Association, said performance-raising schemes over the border had little political support in Wales.
Geraint Davies, secretary of teachers' union the NASUWT Cymru, said a direct injection of capital was now vital. The Assembly says it has provided pound;3 million to local authorities each year since 2003-4 through special grants to support improvement in low-performing schools.
However, Rhys Williams, for NUT Cymru, said struggling schools in Wales had lost local government expertise since the shake-up of boundaries in 1996.
And an Assembly spokesperson said local education authorities should provide tailored support to schools.