SYDNEY, May 3 - The Berejiklian government on Wednesday said NSW didn't have the capacity to make up the shortfall, and called on the federal government to "honour the deal that's already been struck".

"NSW doesn't shy away from the fact we expect the original agreements and funding arrangements we signed up to be delivered," Premier Gladys Berejiklian told the National Press Club in Sydney.

The premier did, however, say she was "heartened by the federal government's commitment to needs-based funding" going forward.

NSW Education Minister Rob Stokes said Canberra's abandonment of the original Gonski deal would result in "millions and millions less than we were expecting (going) into schools in NSW over the next two years".

"Our frustration and our disappointment is we have certain legitimate expectations - in fact, a promise of increased funding over next year and the year after that - and it looks as if we are going to be sorely disappointed," Stokes told ABC TV.

The NSW government is currently seeking legal advice, but Stokes noted legal action was not "something we would like to do".

The state minister will meet his federal counterpart later on Wednesday to discuss the plan but he says so far "the level of consultation has not been ideal".

Federal Labor says the federal coalition's new plan - dubbed Gonski 2.0 - is "friendless".

"The Catholic schools system has been very critical of these changes, so has Rob Stokes, the Liberal education minister here in NSW, so has James Merlino in Victoria and Kate Jones in Queensland," opposition education spokeswoman Tanya Plibersek told reporters in Sydney.

"You go around the states and territories and education ministers - conservative or Labor - who are responsible for funding government schools are saying this is unacceptable."

The NSW Teachers Federation says abandoning the final years of the original Gonski deal will lead to a dramatic cut in funding over the next few years.

"The Gonski agreements would deliver $3.8 billion over 2018 and 2019 but Turnbull's plan offers just $2 billion over the next four school years," acting president John Lemaire said in a statement.

"The Turnbull government's funding cut will mean a lot more students will miss out on the help they need."