On the first Tuesday of the month, after the kids are asleep, my partner starts baking. This month it was chocolate zucchini cupcakes. He hates cake. He’s up at 10pm slathering cupcakes with chocolate buttercream and hundreds and thousands (so no one will notice the zucchini) so there may be music lessons at our daughter’s public school.

At afternoon recess the next day, parent volunteers at our suburban Sydney school lay out the cakes baked by parents the night before and the children solemnly line up, their gold – or silver – coin growing warm and ever so slightly sweaty in their eager little hands. They drop their coin into an old biscuit tin, and then stalk the cake stand, agonising over their irreversible decision. When recess is over, the parents pack up the stand and re-assemble it in another location, keen to eke every possible dollar out of the post-school rush. The money is collected in the tin, reported to that night’s P&C meeting (at which we consume the rejected cakes) and dutifully banked.

It is through these cake stalls, and a pair of fetes requiring hundreds of volunteer hours from families, that we raise enough money for a music tutor to visit our tiny school one day a week. It is raised dollar by dollar. Cupcake by cupcake. We count ourselves fortunate that we have parents who understand the value of music education for young students and have the capacity to fundraise for it.

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Recently we hit our target. The principal announced to the children lined up one morning that they would be able to have their music tutor come back and teach them again next year. The kids cheered.

A couple of days after our last cake stall, it was reported that Knox Grammar had just opened a $47m new facility, including a performing arts centre housing a 750-seat auditorium, purpose-built dance studio and soundproof rooms for one-on-one musical tuition – no doubt funded in large part by parent and community fundraising, just like my own little school. Although when that school talks about hundreds and thousands, it means dollars, not sprinkles.

One can’t begrudge the children at Knox their professional quality soundproof recording studio. Nor the Presbyterian Ladies College its orchestra lift, nor Scots’ $29m castle-esque library. It must be a fine experience indeed to learn and grow in those schools.

Should parents have the capacity and desire to pay and fundraise for those facilities, they have the right to do so. Those same parents also have the right to expect, should they decide not to, that their local public school will be adequately funded to provide their children with a quality education in a safe and comfortable environment. That their public school will be able to pay for quality teachers, that their local public school won’t house their children in hot demountable buildings. The choice between sending children to a public or private school should be about the bells and whistles, not the basics.

The ABC revealed last year that one in three private schools now receive more funding from government than comparable public schools (albeit, many of these private schools are low-fee-charging Catholic schools), a rise from one in 20 ten years earlier. In real terms, according to the Grattan Institute, government funding of all schools has increased by about $8bn over the last decade, but 80% of that growth went to the independent schools sector.

There is a role for government funding of the private school system, which educates a substantial chunk of Australian children. But public assets, public schools open to every single child in this country, needs to be a priority in public spending – especially when those public schools do most of the difficult work in supporting our most disadvantaged young people.

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Otherwise we risk talking not about two different sectors of education, but different strata.

Inequity in education leads to longer term inequality. An OECD report released in October surmised that “the academic performance gap between advantaged and disadvantaged children develops from as early as 10 years old and widens throughout students’ lives”. When those disadvantaged students, however, are placed in a non-disadvantaged school their performance improved markedly. Inequity in education matters, and it matters for a long time.

Private schools are aspirational, and teach well. But public schools too must be the home of aspiration, not where you end up if you can’t afford to go anywhere else. Education is an act of social aspiration; in which we decide as a society that all our children deserve the best possible opportunity to learn, develop and be exposed to one another. If we don’t address inequity when we can, then we will all suffer the consequences of inequality when it’s too late.

• Celina Ribeiro is a freelance journalist based in Sydney