The Archbishop of Sydney has defended the right of religious schools to discriminate, claiming it is integral to religious freedom in Australia.
The Australia Institute has found private schools in New South Wales and Victoria are exempt from anti-discrimination laws and therefore can legally expel gay or pregnant students.
The Institute and the Australian Education Union have called for the exemption to be removed to bring private schools in line with the values of the general community.
But Cardinal George Pell says the Catholic Church should not be coerced into implementing other values.
"We have a right to teach our Christian teachings and to follow out the consequences of that," he said.
"Nobody is forced to send their children to Catholic schools.
"Parents send children to Catholic schools because they know they will get a certain set of values there."