CANBERRA, April 17 - The Abbott Government plans to boost school funding in line with inflation from 2017, but Catholic schools say that's only about half as much as actual costs.

The National Catholic Education Commission says without sustainable funding, schools will be forced to lift fees or close, putting extra pressure on the public system when students inevitably transfer because parents can't afford the higher fees.

Teachers say all schools will be hit with real cuts if the government persists with its plan and the most disadvantaged will feel them most.

The Australian Education Union repeated calls for a return to needs-based funding in line with Labor's Gonski model.

AAP