The average public school student could receive up to $100 less a year in state and federal government funding than a similar independent school student by 2020 without the final two years of Gonski reforms, a new report has revealed.

The "Private school, public cost" report, due to be released on Friday by the former president of the NSW Secondary Principals Council, Chris Bonnor, and education researcher Bernie Shepherd, has found that state and federal government funding for nearly half of the nation's independent schools could outstrip public funding for the average public school within the next five years.

Money for new schools and upgrades... Credit:Photo: Quentin Jones

The reports authors also found that public funding for up to 75 per cent of Catholic schools across the country would outstrip funding for similar public schools by 2016.