New data has highlighted a "shocking disparity" in funding between private schools and public schools.
Challenges of this inequity are being particularly pronounced in rural communities.
The Australian Education Union (AEU) is calling for urgent funding to address the shortfalls after a report highlighted that more than 98 per cent of private schools were overfunded, while more than 98 per cent of public schools were underfunded.
It said the data, released by the Australian Curriculum Assessment and Reporting Authority (ACARA) last week, highlights an urgent need for greater public school funding.
“Public schools enrol the overwhelming majority of Australian students and a greater proportion of students with additional needs,” AEU deputy federal president Meredith Peace said.
“And yet, as this data shows, public schools are being left behind due to inequitable funding arrangements”
The figures are according to the Schooling Resource Standard, agreed to by all Australian governments in 2012 as the minimum to provide a baseline education to students.
But outside the big cities, the difficulties posed by this funding disparity are particularly pronounced for public schools in rural areas.
NSW Teachers Federation president Angelo Gavrielatos told the Pastoral Times "the challenges of this inequity are aggravated in rural communities”, including Deniliquin and district.
He said there are complexities that set them apart from major population centres, and therefore require additional investment.
"In order to close the student achievement gap between rural communities and larger population centres, governments must address these specific resourcing needs,” he said.
“If not, we'll see a deepening inequality and segregation of education, the consequences of which will be far-reaching, not only for individual students but our society as a whole.”
Mr Gavrielatos said the inequity of funding private schools “at the expense of public schools” gathered pace during the Howard government and accelerated during the last 10 years of state and federal Coalition government policies.
“We have seen greater increases in funding to private schools while public schools remain at 90 per cent of their Schooling Resource Standard – the agreed minimum level of funding considered necessary for all students to achieve their very best,” he said.
The NSW Department of Education said it will be working closely with the Commonwealth Government to bring about a fair funding outcome for public schools.
“The greatest positive influence on student engagement and education outcomes is quality teaching,” a department spokesperson said.
“That’s why we are looking to support teachers with providing more admin staff to allow them more time to teach, working to increase their pay to reflect the value we place on them and employing more teachers and school counsellors through the Education Future Fund.”