Former NSW education minister Adrian Piccoli - one of the strongest champions of the original Gonski agreements - has broken ranks with his own government to support the Turnbull government's new school funding model.
Mr Piccoli told Fairfax Media it would be the "biggest own goal in education history" if Labor, the Greens and the Senate crossbench unite to vote down the government's bill this week.
Mr Piccoli's stance contrasts with that of his successor as education minister, Rob Stokes, who has said anything less than delivery of the full six-year Gonski deals was unacceptable to NSW.
Mr Piccoli's intervention came after Fairfax Media revealed secret modelling shows public schools would lose up to $4 billion over a decade if the new model is voted down while Catholic schools would be $4.6 billion better off.
"We have arrived at a crucial moment for education funding and I am calling on Labor and the Greens not to play obstructionist politics," Mr Piccoli said.
"[Former premier] Barry O'Farrell and I were under enormous political pressure from Tony Abbott when we signed up to a deal with Julia Gillard in 2013 but we did it to get the best outcomes for kids in our state.
"I was applauded by the left for working with Labor and taking on my own side of politics.
"Now I want Labor and the Greens to return the favour and do a deal with the Coalition government for the good of our schoolchildren."
The Nationals MP was a passionate defender of public schools during his six years as education minister and regularly attacked the federal Coalition's schools policies.
Mr Piccoli said the amount of money offered by the federal government was still too low, but it was vital to remove the distortions in the current funding system that benefit private and Catholic schools.
The Turnbull government's plan would leave around 400 private schools worse off than under current arrangements and slash funding immediately to 24 mostly high-fee schools.
"If Labor wins office and wants to put more money into schools that's great - there needs to be more money," he said.
"But they shouldn't vote the new model down.
"It's in the interests of our children to have a fair funding model and this model makes it fairer.
"If this isn't achieved this week I don't think it will be for 20 to 30 years."
The government is increasingly hopeful of either striking a deal with the Senate crossbench or the Greens to pass its school funding changes before Parliament rises for the long winter break.
Mr Piccoli said influential public sector teachers unions were making a massive mistake by urging the Senate to block the bill.
"I always had a good relationship with the unions but it would be the biggest own goal in education history if they convince the Greens and others to sink these changes," he said.
"Schools they have complained for years about being overfunded would continue to get too much money."
Mr Piccoli said the new funding model would finally do away with two historic mistakes in education policy: John Howard's decision to maintain funding for over-funded private schools and Ms Gillard's insistence that no school would lose a dollar under her reforms.
Mr Piccoli lost his spot in the ministry in a January reshuffle and moved to the backbench.
Labor education spokeswoman Tanya Plibersek said Labor would not support the government's changes and remained committed to the original agreements.
"The NSW Liberal government, to its credit, has been leading the charge against Malcolm Turnbull's decision to rip $846 million from its state's public schools," she said.
The Greens have been negotiating intensely with the government on a deal that could boost spending on public schools and speed up the funding timeframe but have not announced a final position.
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