The NSW government will find an extra $712 million for state schools after the federal government refused to match its recent $1.2 national "choice" fund for private schools.

NSW Education Minister Rob Stokes had been lobbying the federal government to boost public funding according to the Gonski principles of sector blindness.

The federal government had told states it would withhold all independent school funding if a deal wasn’t signed by December 7, so, with the federal government refusing to budge, NSW decided to match the NSW portion of the choice fund itself.

"In the absence of this, the NSW government has stepped in to provide additional funding to government schools to ensure this historic funding agreement treats all NSW students fairly," Mr Stokes said.

It signed the bilateral agreement on Wednesday morning, becoming the second state to do so.

Premier Gladys Berejiklian said the commitment would mean the NSW government would spend an extra $6.4 billion on state schools over the next 10 years.