That's despite taxpayers contributing large amounts to support the one-in-three students nationwide that attend private schools or non-government schools, according to a Blueprint Institute report released on Thursday.
"The taxpayer spends $18 billion per year on funding private schools under the guise of providing 'educational choice' to families," Blueprint chief executive David Cross said.
"But this justification becomes indefensible when that choice is removed unless families take on credit card debt or remortgage their homes to pay for school."
In Sydney and Melbourne, independent school fees increased by 54 per cent from 2010 to 2020.
About half of independent schools and three-quarters of Catholic school funding comes from state and federal governments, with the bulk of the funding falling on the shoulders of the federal government.
The report alleges independent schools are "increasingly focused on spending money raised from school fees on projects with no educational purpose, such as superfluous capital works, sporting equipment, and overseas travel".
It also noted there has been an excess in salaries for top administrators, claiming the principal of The King's School in Parramatta in western Sydney taking home $700,000 per year.
The same school - which charges day students up to $40,000 a year and up to $68,000 for boarders - reportedly reaped over $8 million in JobKeeper payments from the federal government in 2020 at the height of the pandemic.
AAP contacted the Independent Education Union of Australia NSW/ACT for a comment.
Mr Cross called for greater transparency about funding and how it directly benefits students as a measure of accountability to financially stretched parents and taxpayers.
"The lack of transparency around non-government school expenditure presently means that funds raised from school fees are often used on significant expenses that neither parents nor government are aware of.
"This feeds into the uncontrolled year-on-year fee increases."
The report suggests creating independent transparency advisory committees for each state that monitors expenditures.Â
"Non-government schools will be more reluctant to spend money earned from fees on superfluous capital works, exorbitant executive salaries, travel, and luxury items if they know they have to publicly defend said expenses to the committee and fee-paying parents," Mr Cross said.
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