For it could of course be the correlates which drive this effect:
Pupils raised in religious homes are more likely to succeed, regardless of whether they went to faith school or not, a study has found.
Research by the UCL Institute of Education found that pupils from Catholic and Church of England families did well because of their upbringing, not because of their school.
At best, researchers found, attending a religious school was associated with better results at O-Level, but did not affect how well the pupils did at A-Level or university.
For a cohort born in 1970 they analysed pupils’ religious upbringing and the school they went to and found that while Christian pupils at Church of England and Catholic schools did better, this became statistically insignificant when the positive impact of their religious upbringing was factored in.
And they’re right in part at least, it could be correlates:
“The much-vaunted ‘Catholic school effect’ was mostly explained by the fact that Catholic school pupils were usually from Catholic homes.”
The paper suggests that stricter parenting, the protective influence of being part of a faith community, or for Catholics, being of Irish immigrant heritage, could be behind the advantage.
“It is well established that immigrant and ethnic minority groups manifest high rates of educational persistence, staying on in further and higher education at higher rates than ethnic majority peers with similar levels of prior attainment,” the study argues.
Professor Sullivan added: “We can speculate that the academic advantage of a religious upbringing at home may be due to cultural differences, such as differences in parenting practices and attitudes to education, as well as to religious belief or practice itself.
“For example British Catholics at this time were often of Irish or European origin, bringing different cultural norms to those raised in other faiths, or none.”
Not that it would be PC to do this but it could be that a greater propensity to maintain the nuclear family has some sort of effect. You know, maybe? But think on the difficulty of getting that result published….