Children in three Welsh education authorities have been significantly underachieving at GCSE over the past five years, a TES Cymru analysis has revealed. But three other LEAs have consistently performed well above expectations, given the proportion of children entitled to free school meals.
Wrexham, Monmouthshire and Flintshire are the authorities where pupils have been underachieving. Children in Neath Port Talbot, Ceredigion and Gwynedd have, however, exceeded expectations.
TES Cymru looked at Assembly government statistics comparing the percentage of pupils gaining at least five A*-C grade GCSEs with the figures for free meal entitlement. If performance had been in line with predictions, leafy Monmouthshire would have been challenging the equally middle-class Vale of Glamorgan for the highest percentage gaining five or more good GCSEs last summer.
Instead, it could manage only 53 per cent (predicted 60) compared to Vale's 63 per cent (predicted 61) and a Welsh average of 51. In Flintshire, 59 per cent of candidates were expected to reach the GCSE benchmark last year but only 55 per cent did.
In Wrexham, the gap between expected and actual results was nine percentage points last year. Only 45 per cent of pupils achieved at least five good GCSE passes against a predicted 54.
John Roberts, senior secondary education officer in Wrexham, said improvements were expected following the employment last September of dedicated learning and teaching advisers in English, Welsh, maths and science. Previously, advisers were shared with 32 secondaries across north Wales, and had "difficulty getting to grips with individual schools and departments".
Wrexham is also making extensive use of data analysis by the Fischer Family Trust - which predicts pupils' likely performance given previous attainment and free school meals entitlement - to set individual, departmental, school and LEA targets.
"We have already identified that the Achilles' heel in Wrexham is middle-ability pupils. We are doing well with lower and higher-ability pupils," said Mr Roberts.
Neath Port Talbot, in the deprived south Wales valleys, was consistently the biggest overachiever: last year, 55 per cent of pupils got five or more good GCSEs, compared to a predicted 46 per cent. Ceredigion (61 per cent) and Gwynedd (60 per cent) also did well as both were expecting 56 per cent.
Kathleen Boyce, head of Neath Port Talbot's schools, education, development and inclusion service, said: "We are very pleased that schools have added value to pupil performance because this enables young people to have a wider choice of future education, training and careers.
"We are confident that further improvements will be possible because recent inspections indicate that our primary and secondary schools give top-quality care and support to their pupils."
The relationship between deprivation and achievement is well-established - as the proportion of free school meals rises, results generally decline.
Unions and some academics say funding can make a difference. But the fact that some Welsh LEAs are achieving above expectations despite lower levels of per-pupil spending, suggests other factors are at play.
David Reynolds, professor of education at Exeter university, an expert on funding issues in Wales, said an independent study was needed to explain the funding and performance relationship.
He said: "The lowest-performing LEAs are generally among the low spenders.
Yet the Vale of Glamorgan has been overshooting against expectations for years despite historically being the lowest spender. It's a question of the resources available or the management of those resources, or both. We need to find out."