Non-religious parents have admitted to baptising their children to get them into Catholic schools in Sydney's eastern suburbs, The Daily Telegraph reports.
Sydney Catholic Schools spokesman Mark Rix said about 90 percent of Catholic schools in Sydney's eastern suburbs are "full or close to full" and they predicted enrolments to grow from 21,424 to 23,009 by 2021, or about 317 students a year.
Mr Rix warned schools would struggle to absorb the increase unless the Government stumps up more cash for capital works.
He said they were looking for potential sites to build a new school in the east but they were "hopeful" of more funding from the Government to help them achieve this.
A Bondi mother said she got all three of her children baptised for the sole purpose of being able to send them to St Charles Catholic Primary School where they also learned the sacraments.
"We are atheist but I couldn't afford the private schools and I didn't want to put them into the public sector," she said.
Two of her children have already left school but one of her sons is still at Waverley College.
"He doesn't believe in God but he loves the social and sporting elements at the school."
Waverley College head Ray Paxton said their school was welcoming and inclusive of families from other faiths.
"While preference is given to Catholic enrolments, we believe non-Catholic/non-Christian families enrich our school community.
"Our enrolment interviews ask all families to consider the contribution they will make to the religious dimension of the college.
"During these conversations, we have found the values of the majority of families are congruent with the Christian and Catholic values of our school."
Enrolled, Catholic students are invited to participate in the sacraments but it is not compulsory, he said.
The Catholic Education Commission NSW estimated 2035 extra classrooms would be needed to cope with an increase in Catholic enrolments across the state by 57,000 students between 2015 and 2031, or about 3350 students a year.
A spokesman for the Federal Education Department said capital funding for non-Government schools was allocated on the basis of student enrolments and need.