The New South Wales Government says it will not sign up to any school funding model that offers "special deals" for Catholic and independent schools.

Key points: The Federal Government is changing the way independent schools are funded

The Federal Government is changing the way independent schools are funded Under the new model announced, school funding will be tied directly to parental income.

Under the new model announced, school funding will be tied directly to parental income. NSW Education Minister Rob Stokes is not happy about the changes

In a blow to Prime Minister Scott Morrison's revamped education funding model, NSW Education Minister Rob Stokes said the promise of an extra $4.5 billion over 10 years in federal cash for independent schools was "not fair".

Mr Stokes said he had "no advanced warning" of the deal.

"We welcome additional money into NSW schools — our simple message is, it's got to be distributed fairly," Mr Stokes said.

Mr Stokes said he was "puzzled" by the announcement, because the NSW Liberal Government and the Federal Government "were pretty close to a deal ... on the basis that there would be no special deals" and that "money would be allocated according to Gonski principles".

"New South Wales public schools are the largest by far of any of the sectors, you can't leave them out, it's just not fair," he said.

Data from the Australian Bureau of Statistics [ABS] showed as of last year, the bulk of students across the nation are enrolled in government schools at 65.6 per cent.

Following this, 19.9 per cent of students are enrolled in Catholic schools and 14.5 per cent in independent schools.

It is not the first time Mr Stokes has criticised his federal coalition colleagues' education policies.

In May, he told the Federal Government NAPLAN testing should be dumped, while he also sided with Labor and the Greens in criticising the "Gonski 2.0" blueprint.

'There is nothing Christian about it'

The NSW Education Minister Rob Stokes has hit out at Prime Minister Scott Morrison's "special deal" brokered with Catholic and independent schools. ( ABC News: Matt Roberts )

The Federal Government's decision shows a move away from a funding model based on census data, to one based on tax data to calculate a school's wealth.

Under the changes, independent school funding will be tied directly to parental income.

The stoush escalated on radio this morning when Mr Stokes and Mr Morrison conducted parallel interviews with the ABC.

While Mr Stokes criticised the new funding model on ABC Radio Sydney, Mr Morrison was giving an interview on Radio National where he said: "I don't think Rob's had the chance to look at the full details of this."

Shortly after, Mr Morrison's comments were played to Mr Stokes, who did not back down.

"It certainly appears that more money is being provided to independent and Catholic schools and that no additional money other than what was already on the table is being provided to NSW public schools," he said.

"If that's the case, which is certainly appears to be, well clearly that's not fair."

Mr Morrison said needs-based funding model for public schools remained, and that the deal with the Catholic and independent schools sector would "sit outside" the previous arrangements.

NSW Education Minister Rob Stokes was critical of the funding changes. ( AAP: Brendan Esposito )

It is expected that the new funding calculations will be brought in from 2020, according to a recent review by the National School Resourcing Board.

Former NSW Education Minister Adrian Piccoli blasted the decision to give private schools billions of dollars of extra funding.

"This is pathetic. There is nothing fair about it. There is nothing Christian about it. It's throwing money at the powerful and well connected," he wrote.

Mr Piccoli was NSW's education minister between 2008 and 2016.

He resigned from Parliament after losing the portfolio in a 2017 cabinet reshuffle and is now the director of the Gonski Institute for Education.

Teachers union blasts 'attempt to buy votes'

The NSW Teachers Federation backed Mr Stokes and slammed the Federal Government's funding proposal as "corrupt".

In a statement, the federation's president Maurie Mulheron called the funding boost "an attempt to buy votes ahead of the next federal election".

"This is inequitable, unfair and a corrupt funding model," Mr Mulheron said, adding that the Prime Minister "ought to be taking notice" of Mr Stokes' rejection of the funding allocation.

"The Federal Government has ripped billions of dollars from our public schools. We want public school students to have smaller class sizes, more one-on-one support and additional teachers and support staff," he said.

According to ABS figures, teachers in public schools are responsible for teaching 74 per cent of children in outer regional areas, 77.5 per cent of children in remote areas, and 88 per cent in very remote areas

"Public schools have always done the heavy lifting and, as a consequence have the greatest need for additional resources," Mr Mulheron said.

"But Scott Morrison and Federal Education Minister Dan Tehan are ignoring the needs of public schools, public school students and their teachers."