Thousands of striking teachers have marched on South Australia's parliament house to demand better pay and conditions as relations between the union and the government curdle.
It was the second strike by Australian Education Union (AEU) members in two months as discussions between the parties over a new enterprise bargaining agreement appear to have reached a deadlock.
AEU SA branch president Andrew Gohl threatened further industrial action if the government does not deliver increased pay and reduced workloads.
"We have 1,800 students in South Australia right at this very moment who have no regular teacher in front of them," he told crowds massed before the steps of parliament on Thursday.
"This is a government that is fixed on the short term and political imperative without a view to what's best for South Australian people, what's best for public education in the long term."
Hundreds of schools across the state shut their doors or offered modified classes, but South Australian Certificate of Education (SACE) physics and accounting exams for about 1,000 year 12 students went ahead as planned.
The AEU had given Peter Malinauskas' government an ultimatum to present an improved pay offer by Monday, but the revised proposal of a 4 per cent increase in year one, 3 per cent in year two and 2.5 per cent in year three only served to rile the union further.
"(This is) the only place in Australia where a third offer could possibly get worse than the second," Gohl said.
Education Minister Blair Boyer is still working to reach an agreement with teachers.
The government's previous offer of three pay rises of 3 per cent over three years also included two one-off $1,500 payments, meaning many lower-paid teachers would be worse off under the new deal.
South Australian teachers are currently the lowest paid in the country, with graduates earning less than $75,000.
Earlier this year their NSW counterparts won an historic wage increase, including a rise of more than 12 per cent for teachers straight out of university.
The union has also taken umbrage with the government's refusal to bring forward a seven-year delay to implement a reduction in teaching hours, arguing teachers are in desperate need of workload relief and cannot afford to wait that long.
Martin Westwell, chief executive of the Department for Education, said it was disappointing the union had decided to take industrial action instead of sitting down at the negotiating table.
On Tuesday Boyer said he was shocked by the union's refusal to call off the strike but was eager to maintain a positive relationship with Gohl to progress a final agreement.
The Greens called on Labor to impose a levy on the big banks to find the money needed to fix a public school system "at breaking point".
"The Malinauskas government should be prioritising funding for public schools and their teachers," Greens treasury spokesman Robert Simms said.