Parents are contributing $1 billion each year to state schools, as principals increasingly look to families to prop up the costs of public education.

Key points: Figures reveal just how much parents of public schoolkids are shelling out for education

Figures reveal just how much parents of public schoolkids are shelling out for education They're paying more than $1billion for activities and hygiene products

They're paying more than $1billion for activities and hygiene products The NSW Parents and Citizens Federation says there should be no fees for public education

The billion-dollar outlay includes cash contributions from parents as well as the invoiced costs of some subjects, excursions, educational product subscriptions and even hygiene products such as tissues.

Many schools are looking to external providers to deliver school sport, music and drama programs in a bid to pass on some of the costs of public education to parents.

Schools also routinely bill parents for the cost of hygiene products including soap, tissues and cleaning costs.

Sydney mother Lisa Polsek, whose two daughters have been educated in public schools, said costs had been rising.

"The principle, in my opinion, is that public schools should be what they are, publicly funded schools, so why would you need parents to keep giving you money for something that's supposed to be coming from the Government and from people's tax monies?" she said.

Lisa Polsek said school fees at her children's school have risen over the past two years. ( ABC News: Brendan Esposito )

The Parents and Citizens Federation of New South Wales said it had raised the issue with the NSW Education Department that some public schools were invoicing parents for excessive fees, in one case as much as $1,500 per term.

It follows one notorious case in NSW of a school principal offering free popcorn to children whose parents had paid fees on time, while students whose parents had not paid missed out.

"We've [noticed] an observable increase in schools taking the approach of charging what appear to be compulsory fees to parents, and taking it to the point where some of those fees are well and truly above what you would expect," Tim Spencer, vice-president of the P&C Federation of NSW, said.

"Our viewpoint is that there should be no fees at all with public education.

"It's very clear in the Education Act that the Government should provide free education to public schools."

NSW tops the list, collecting $371m from parents

According to the latest figures published by the Australian Curriculum and Assessment Authority, the total amount of income schools around the country collected from fees, charges and parent contributions totalled $1.03 billion in 2016.

NSW public schools received the most money from parents — $371 million in 2016.

Queensland schools collected nearly $216 million from parents, Victorian schools collected $207 million, followed by South Australia at $104 million, and WA at $98 million.

The ACT, Tasmania and the NT collected $21 million, $19 million, $5 million respectively from parents.

In NSW, according to department policy, all contributions that schools request from parents are supposed to be voluntary.

But parents say schools do not regard fees as voluntary and expect invoices to be paid, sometimes aggressively chasing up unpaid amounts.

Ms Polsek said she was surprised fees became more expensive as the years progressed, and more and more things were added to the list.

"It definitely seems to me that they're increasing everything that they're asking people to pay for," she said.

"I think parents probably expect that when you go to a public school, you're not going to be asked for those kinds of fees. And they are fees. They don't call them fees but they are."

There is no charge to parents for the compulsory parts of the curriculum in all states, but in NSW, the Education Department allows some subjects to be outsourced to what it calls "enhance teaching and learning".

The department said in a statement:

"NSW public schools can request voluntary contributions to enhance the educational programs that are provided to students. "Principals are to ensure that no student or family suffers any discrimination or embarrassment over failure to make a voluntary or subject contribution."

Some schools outsource sport despite it being part of the compulsory curriculum. ( ABC News: Loretta Florance )

At some schools in Sydney, school sport is now run by external providers and parents are billed an average of $200 per year for the programs.

Parents are billed similar amounts of money for performing arts programs delivered by external providers.

Sport is part of the compulsory curriculum.

"For schools to outsource through third-party providers the teaching of certain parts of the curriculum, that is something which we feel is totally and utterly wrong," Mr Spencer said.