Australia’s public schools will miss out on $13bn in the next five years if accounting tricks are maintained in upcoming funding agreements, a major report has found.

The National School Resourcing Board’s (NSRB) annual review, tabled in parliament last week, showed government schools lost more than $2bn in 2022 because of a Morrison-era loophole that allows states and territories to claim up to 4% of public school funding on non-school expenditures.

The federal education minister, Jason Clare, has indicated the 4% will not be reviewed until the next round of funding agreements – scheduled for 2030.

Modelling provided to Guardian Australia by the Save our Schools convener, Trevor Cobbold, suggests if Clare’s position remains, public schools will miss out on about $13bn in funding to the end of the decade.