Teachers are stepping up their campaign for better school funding after Malcolm Turnbull's income tax plan.
The prime minister wants to reduce the federal government's income tax collection by about $14 billion and allow states and territories to levy the same amount to pay for schools and hospitals.
The Commonwealth would then reduce the grants it hands to the states to keep its budget in check.
Mr Turnbull says no federal government would ever walk away from supporting the non-government school sector.
But he said on Thursday the future funding of government schools is "bound up in this discussion of more fundamental revenue sharing reform", referring to the income tax plan.
Australian Education Union deputy president Maurie Mulheron said the prime minister's comments appeared to confirm the end of federal funding of government schools under the coalition.
"Locking in a system where state governments have full responsibility for public schools and the federal government for private schools is locking in inequity and would be the end of needs-based Gonski funding," Mr Mulheron said.
"Schools don't care whether their funding comes from the state or federal government - they just care about whether they have the funds to meet the needs of their students."
Under the Gonski plan, which Labor supports, two-thirds of extra schools revenue was to have come from the federal government and a third from the states.
The federal government would take most of the responsibility for supporting disadvantaged schools.
It's estimated this would cost an extra $4.5 billion in 2018 and 2019.
With the school funding issue back in the public arena, the "I Give a Gonski" campaign will be stepped up with television ads in Sydney, Canberra and Brisbane in the coming week, as well as print and digital advertising.
Marginal seat doorknocking is also under way.
Campaigning would continue at least up to the budget on May 3, a union source said.
Labor leader Bill Shorten said Mr Turnbull should not wash his hands of education funding.
"There are few things as important as education to the future prosperity of this country," Mr Shorten said.
