England’s pupils are consistently outperforming their Welsh peers in core school subjects, according to thinktank the Education Policy Institute.

Its study found that children in the two countries performed similarly between 1995 and 2002. Wales gained control of its education system at the end of the 90s, and from the mid-2000s their fortunes started to diverge.

By 2011-12, 82 per cent of children were achieving grade A*-C at GCSE in England compared with 73 per cent in Wales.

Around 10 per cent fewer children also achieved a grade C or higher in English and maths in Wales in 2012-13, compared with in England.

The comparison held true all the way through school, according to EPI’s analysis of data from the Millennium Cohort Study of pupils at ages 3, 5, 7, 11 and 14.

While the children performed to a similar level in their early years, those in Wales started to fall behind at age 7 and again at 14.

Difference ‘not down to disadvantage’

Similarly, the report found that English pupils’ English and maths scores have been in line with the average across the Organisation for Economic Cooperation and Development in recent years, while “performance in Wales has been consistently below”.

“There seems to be clear evidence from a range of sources to suggest that teenagers in Wales display worse educational outcomes than children in England,” said EPI.

“This is seen across a range of sources - GCSE results, Pisa [Programme for International Student Assessment] tests, cognitive tests in surveys - and is common to disadvantaged and less disadvantaged pupils alike.”

One possible reason for the disparity is the difference in demographics between the two countries.

Wales has more persistent child poverty than England and a smaller share of ethnic minority pupils, who tend to perform better at GCSEs.

“England is a country with a population of 55 million people, including large numbers who live in wealthy areas... while Wales is a country of 3 million people with many areas of significant disadvantage,” said Tim Pratt, director of the Association of School and College Leaders Cymru.

“Pupils in areas of high disadvantage face similar challenges wherever they live, and their performance in exams and tests is likely to be similarly affected.”

However, the EPI found that even when comparing the performance of children on free school meals, those in England still outperformed their Welsh peers.

“Lower level of performance remains for disadvantaged pupils in Wales, even after the GCSE rule changes in England in 2014,” said the report.

“This simple comparison suggests that differences in deprivation are unlikely to explain lower levels of performance in Wales on their own.”

The EPI said it plans to undertake more in-depth research to explain the different rates of progress, as England and Wales embark on separate GCSE reforms.