South Australia's private schools only achieve the same results as comparable public schools, despite spending almost $180 million more a year more on their students.
Analysis by researchers Chris Bonnor and Bernie Shepherd, prepared for Australian Greens Senator for South Australia Penny Wright, shows almost a quarter of government funding to private schools is in excess of what it costs to educate similar students in public schools.
Senator Wright said the research highlighted the staggering inequality in school funding, and argued the excess funding should be redirected to disadvantaged schools in South Australia.
"In Australia, the best indicator of education success is family wealth, not ability. That's just appalling in a country that prides itself on a fair go," she said.
"But report after report is showing us we can absolutely turn this around if we stop funnelling money to privileged students and invest that money to target disadvantaged students and schools.
"Some of Adelaide's private schools spend almost twice as much per student than comparable public schools - that's more than $10,000 per student - but still only achieve the same academic outcomes.
"If all this extra cash is not delivering better results, I think it's very fair to ask if that money could be better spent elsewhere in the education system.
"If we narrow the equity gap, South Australia's educational outcomes will go through the roof - and that will deliver huge economic benefits to our state."