His parents then chose The Emanuel School in Randwick simply because they thought he would be better off there than any of the other local schools. ''As soon as I went to Emanuel, because it was so small and there were girls there, I became more focused … it was a great school to go to,'' he says. Having no religious conviction is increasingly common in Australia. A record 22 per cent of the country indicated as much in the 2011 census. Yet the popularity of religious schools is increasing. Enrolments in independent and Catholic schools are growing faster than at public schools, increasing by about 1.8 per cent in 2012, compared with 1.2 per cent for public schools, according to recent data from the Australian Bureau of Statistics. ''It's one of the great paradoxes of Australian education,'' says Dr Helen Proctor, from the University of Sydney. ''We're one of the least-religious nations in the world, yet we have this large and increasing attendance of children in religious schools.''

Proctor was the co-author of the 2009 book School Choice: How Parents Negotiate the New School Markets in Australia, for which she interviewed many non-religious parents about why they sent their children to religious schools. ''What they were trying to choose was a non-public school because they were disaffected with public schools, one way or the other,'' she says. In Australia, almost all private schools have some religious affiliation. The choice is often akin to a''cost-benefit analysis'', she says. ''The benefit was that it's a private school - it's got good facilities, good academic results, nice new buildings and the cost might be that it's a bit religious.'' John (not his real name), a Sydney father and lapsed Catholic, says he and his wife had their three children baptised for the sole reason that it may eventually help them secure a place at a Catholic high school. ''Philosophically, we would prefer to have a secular government education for our children,'' he says. But John says he would not send his son to the local public boys' high school, which he believes has a poor reputation, particularly where discipline is concerned. He feels his son will perform better academically at a private school.

''I don't necessarily want them to have a religious education, that troubles me a little bit,'' John says. ''It's a trade-off, but I think we'd probably have some conversations at home about what he's doing at school, what his view is, what our view is. ''When you have kids you try to make the best decision you can for them, not what you philosophically believe.'' Children from atheist families are generally welcome at most religious schools, provided they participate in the religious aspects of school life, some education officials say. ''We very much encourage families, all families, to consider a Catholic education for their child,'' says the executive director of Catholic schools for the Archdiocese of Sydney, Dan White. White says that while preference is still given to Catholic families, about one in five students at Sydney Catholic schools comes from other faith backgrounds or is not religious.

''There's a very strong view that we are welcoming and inclusive of families from other religious traditions as long as they understand their child will be taught within the Catholic tradition,'' he says. The 17 schools administered by the Sydney Anglican Schools Corporation have an open enrolments policy. But like Catholic schools, all students are expected to participate in religious activities, such as chapel. ''We're very up front about our Anglican faith traditions,'' says spokesman Andrew Guile. Emanuel principal Anne Hastings says the school embraces all streams and customs of Judaism and offers places to students of other denominations as part of its commitment to egalitarianism and pluralism. Students are expected to enrol in Jewish studies until the end of year 11 and take part in some mandatory cultural activities, Hastings says. ''We do not view Judaism exclusively as a religion but also embrace it as a tradition, culture and national identity,'' she says.

As a student at Emanuel, Sharp sometimes wore a yarmulke and prayed in Hebrew. The experience gave him a respect for religion and made him question his atheism, he says. ''I went in an atheist but came out an agnostic,'' Sharp says. White says parents who choose to enrol their children at Catholic-run schools should expect Catholicism to play a role in other areas of the curriculum, such as sex education or in teaching principles of social justice. ''In areas of sexuality they would bring a Catholic perspective to those questions, they would also infuse Catholic values across the curriculum,'' White says. ''There's a very strong dimension of social justice in Catholic schools whether in history, science, climate change and ecology.''

Sydney mother-of-two Jenny (not her real name) says she does not regret sending her two children to Catholic high schools. She was particularly pleased with the strong emphasis on social justice at her son's Marist school. ''[He] had a very progressive Catholic school … It was a non-homophobic school; kids at his school came out,'' she says. Proctor says the emphasis on social justice or charity is a positive cited by many parents who choose religious schools. But a similar value set led other parents, even the strongly religious, to secular public schools, she says. ''One parent I spoke to who was quite a religious Islamic woman preferred to have her kids at a public school,'' Proctor says. ''She felt that her faith was a matter for the family and at the school she was looking for diversity and an understanding of different faiths and cultures.''