For the civil and chemical engineer and his wife Yogarani, also an engineer, the focus for their family was for the children to study with ''like-minded'' students.

Their son, Kajanan, 17, is vice-captain of James Ruse Agricultural High and their daughter, Balaki, is in year 10.

''For us, we gave little thought to private schools because we researched schools and we knew we wanted them to be with like-minded kids and where they could be challenged,'' Mr Parameshwaran said.

Highly educated parents such as Mr Parameshwaran, who migrated from Sri Lanka in 1998, are increasingly sending their children to the state's best selective schools rather than some of Sydney's most elite private schools, the latest My School data reveals.

The top selective schools, including James Ruse, Baulkham Hills, Hornsby Girls and North Sydney Boys, have families from the highest social and educational backgrounds, the index measuring social advantage on My School shows.

As well as the Index of Community Socio-Educational Advantage, My School also publishes every school's distribution of students across the quarters of social advantage. At James Ruse, which has consistently topped the Higher School Certificate results for almost 20 years, 85 per cent of students come from the most advantaged backgrounds and none fall into the most disadvantaged quarter. James Ruse's ICSEA ranking is 1249, while Baulkham Hills has an ICSEA of 1200, Hornsby Girls 1229, North Sydney Boys 1216, North Sydney Girls 1216 and Sydney Girls 1196. The average rank is 1000.

Mr Parameshwaran sent Kajanan and Balaki to their local primary rather than a school with a selective opportunity class but the couple always intended to send them to one of the top-performing selective schools for high school.

An education academic at the University of Sydney, Craig Campbell, who has written a book called School Choice, said private schools considered selective schools a threat and they tried to attract students from advantaged backgrounds

But Dr Campbell said selective schools were ''the most socially exclusive schools of any in NSW''.

As well as a high level of social advantage, many of the selective schools have an extremely high proportion of students with a language background other than English. At James Ruse it is 97 per cent.

''But they also have a very high proportion of parents who are tertiary-educated and also from professional middle-class backgrounds so there is a huge pull of cultural capital,'' Dr Campbell said.

''A lot of the families who were sending their kids to selective schools tended to see some of the wealthier non-government schools as too rich, too privileged.''