The Government is considering advice on different ways of subsidising private schools but has ruled out an increase in next month's Budget.
The schools are currently subsidised from a capped pool of $45 million that does not change with inflation or the number of enrolments.
One option is to remove the cap and give private schools a set percentage of state school funding per student.
The teacher unions and the Principals Federation believe any change will eventually lead to more funding for private schools.
They say if the Government has any more money for schools, it should go to the state sector.