Pupils at faith-based primary schools are a year ahead of children at other schools, research by the National Institute of Economic and Social Research has found.
In a 2002 study by the National Foundation for Educational Research, the value that certain schools add to pupils' learning between the ages of 11 and 16 was examined. It concluded that faith secondary schools have a negligible effect.
But Professor Sig Prais from the institute said the study failed to appreciate how far ahead many children who attended faith schools were by the time they entered secondary school aged 11.
An analysis of key stage 2 maths scores from primaries in the London borough of Barking and Dagenham, where results are similar to the national average, found pupils in religious schools far outperform other children.
On average, using 2003 results, children at the borough's seven faith primaries scored 67.6 out of 100, compared with 53.9 at other schools. It meant faith school pupils had a grasp of maths equivalent to a child aged 12.6, compared to 11.6 elsewhere.
The gap was biggest among children in the bottom 10 per cent at both types of school. Even the worst performers at faith schools had a "maths age" of 10.9, compared to 9.2 at other primaries.
Terry Sanderson, vice-president of the National Secular Society, said:
"These are very simplistic conclusions. Parents have to jump through hoops just to get their children into a church school - it means these children are well ahead of their peers before they go to school, never mind when they leave."
* Faith schools are a threat to social cohesion and should be closed, according to Les Lawrence, education leader at Birmingham council, Britain's biggest inner-city authority. He told the Birmingham Post he would seek to "reduce the number of faith schools" and not encourage more during any school reorganisation within the city.