International research suggests their popularity, increasingly with non-religious families, is based on their ability to outperform secular schools.
Jaap Dronkers, of the Amsterdam School for Social Science Research, gathered together comparisons of the performance of state schools and state-funded religious schools across several countries. In France, where about a fifth of pupils are in religious schools, poorer pupils at Catholic schools benefited from lower drop-out rates and slightly better results.
An analysis of the international test scores of pupils with similar backgrounds in five religious schools, nine public schools and 13 grammar schools in thre German states found pupils in religious schools scored more highly in intelligence tests but did less well in maths and science.
In Hungary, churches are beginning to reclaim schools that were nationalised five decades ago. A survey of pupils in their last year showed that religious schools attained higher grades and had more success in getting students into post-16 education.
About 560 of England's 3,500 secondaries are religious schools, and nearly a quarter of the country's most successful secondaries are run by the church. A 1998 Office for Standards in Education report claimed Catholic and Anglican schools had higher standards and a better quality of education and school climate.
Critics claim the evidence is marginal or mixed, however, and cite "leafy suburb" locations and selection as explanations for the success of faith schools.