Catholic and private school funding grew by more than four times that of public schools in the first three years of the Gonski reforms, a national report by lobby group Save our Schools has found.
Analysis of new data by former Productivity Commission economist and the group's convenor Trevor Cobbold has revealed the long-term scale of state cuts to public schools across Australia, with the ACT singled out for the second biggest reductions in funding per student between 2013 and 2016.
The ACT government has long supported the Gonski model of needs-based funding, becoming one of just three jurisdictions to sign the original deal in 2013.
But by 2016, Mr Cobbold said its total school funding was less than half of the 3% annual increase it had agreed to from 2015. When adjusted for inflation, territory funds for public schools in 2016 had been slashed by $660 per student since the deal was signed, he said.
In the same period, money for independent schools also fell by $140 a student, but Catholic schools received an extra $221per pupil from territory coffers.
An ACT government spokesman said per student funding to most ACT schools was above the schooling resource standard when the original Gonski model was put in place, while almost all other jurisdictions fell below.
"Funding to ACT public schools has been guided by the model gradually trending down to the schooling resource standard," he said.
Under the new Gonski 2.0 deal legislated last year, all jursidictions will see their funding tied to the resource standard in order to "hold the states to account".
The Commonwealth has come under increasing pressure to top up funding in schools since 2013 and Federal Education Minister Simon Birmingham said the new model would draw a "a line in the sand for the cost-shifting that’s carried on in the schools funding debate".
"[The new Gonski deal] will stop states and territories taking increased schools funding from the Commonwealth with one hand and reducing their own contribution with the other," Senator Birmingham said.
Mr Cobbold questioned why only public schools appeared had seen their funding scaled down in the ACT, describing the trend as "shattering".
He said, while governments across the country claimed to be investing in schools each budget cycle, the long-term numbers told a different story.
Mr Cobbold drew on seven-year figures published by the Australian Curriculum, Assessment and Reporting Authority to show combined state and government funding for public schools was cut across all states and territories, except Queensland and Tasmania, between 2009 and 2016.
In 2016, the income of Catholic schools was greater than public schools in all jursidictions except the ACT, where Commonwealth money for Catholic schools increased at ten times the rate of public school funding between 2013 and 2016.
Mr Cobbold said the income divide between state and non-government schools had only widened since the introduction of Gonski, and an immediate and "major funding boost" from state governments was now needed to bridge it.
"This is probably the most comprehensive analysis we’ve done so far....because ACARA have published aggregate figures on state funding for the first time," he said.
In a 2017 Productivity Commission report, the ACT was found to be the highest total spender in the country on public schools, when other factors such as user cost of capital, payroll tax and school transport were included in calculations.
A Save our Schools analysis of the most recent figures ranked the ACT third in Australia for total spending per student in the public school system.
Over the next decade, Senator Birmingham said the Commonwealth would invest an extra $110 million in ACT public schools, at about a 5.8 per cent increase per student each year.
The ACT government has indicated it will continue to invest in school growth and resources in next month’s budget.