Victoria's teachers walk out Thursday as a 28 per cent offer fails to end the fight

Public school staff will strike statewide after knocking back a pay deal the government calls the best in the country, over workloads it says amount to 12 unpaid hours a week.

Victoria's public school teachers will walk off the job on Thursday.

Hundreds of government schools will be affected, after the Australian Education Union's state branch voted on Tuesday to strike.

Teachers will down tools and refuse unpaid overtime unless an eleventh-hour deal is struck with the State Government.

The sticking point is not, on its face, the money.

In June the union knocked back a Labor offer of 28 per cent over four years — a deal the government says would have made Victorian teachers the best paid in the country, with the best conditions, and one the union's own leadership had endorsed before members rejected it.

What the union says the offer did not fix is the workload.

Branch president Justin Mullaly said teachers, principals and support staff were being asked to prop up an underfunded system with their own time.

“In this underfunded system, teachers, principals, and education support staff are working an average of 12 hours unpaid overtime every week,” Mr Mullaly said.

“The government must stop relying on the goodwill of school employees as a core part of their funding model for schools.”

That goodwill, the union argues, is running out.

Mr Mullaly said just three in 10 staff expected to stay in public schools until retirement, many of them citing excessive workloads as the reason they would leave.

He tied it to a shortage already biting: a chronic lack of teachers he said the government had failed to address, in a system where the people still standing are being asked to absorb the gap.

The government wants the union back at the table before families are caught in the middle.

“This deal, which was endorsed by the AEU leadership, would have made Victorian teachers the best paid in the country together with the best conditions,” a government spokesperson said.

“We will always back our hardworking teachers, school leaders and education support staff.”

This is not the first walkout, and it will not be the quietest.

In March, tens of thousands of teachers in union red marched on state parliament — as many as 35,000 — in the first strike of its kind in more than 13 years.

Other action is already in force: a ban on state Labor MPs visiting public schools, and on staff responding to education department emails.

The politics are sharpening with a state election five months out.

Education Minister Ben Carroll has accused the union's leaders of being out of touch with their members. Photo: The Glass

Education Minister Ben Carroll has accused the union's leaders of being out of touch with their own members — endorsing the deal, then failing to sell it — and warned the offer might not stand if a Liberal or One Nation government wins in November.

Opposition education spokesman Brad Rowswell threw the failure back at Mr Carroll, saying Victorian families should not pay the price for Labor's inability to manage the state's finances or close a deal with the workforce that teaches its children.

Between them sits a union representing more than 60,000 teachers, principals and support staff.

On Thursday, they will not be in class.