A SENIOR Anglican bishop calls it "appalling" and a gay and lesbian rights group condemns it as "deeply offensive", but the Attorney-General, John Hatzistergos, backs a NSW law that allows private schools to expel gay students simply for being gay.

Through a spokesman, Mr Hatzistergos, described the 30-year-old law as necessary "to maintain a sometimes delicate balance between protecting individuals from unlawful discrimination while allowing people to practise their own beliefs".

A relic of the Wran era when homosexuality was still a crime, the law exempts private schools from any obligation to enrol or deal fairly with students who are homosexual. An expulsion requires neither disruption, harassment nor even the flaunting of sexuality. Being homosexual is enough.

Introducing the little-known law in the early 1980s, the then attorney-general Paul Landa told Parliament: "The facts of political life require acceptance of the claim of churches to conduct autonomous educational institutions with a special character and faith commitment."

But the churches are now divided. The Anglican bishop of South Sydney, Robert Forsyth, told the Herald: "I don't think our schools would want to use it."