South Australian parents might be left scrambling to care for their children on Thursday when the state's public school teachers walk off the job.
For the first time in a decade, teachers will stop work from the start of the school day until 12:15pm.
It follows a breakdown in enterprise bargaining negotiations between teachers and the SA Government.
"We have over 13,000 members… and an overwhelming majority of our members who participated supported the half-day stop work action," Australia Education Union SA president Howard Spreadbury said.
"Our members don't take industrial action lightly."
Mr Spreadbury said teachers wanted more resources to support their work and their students' learning environments.
"(It shows) how concerned they are at the Government not taking notice of some of the very sensible provisions they've put on the table through us and enterprise bargaining."
Treasurer describes union's claims as 'nonsense'
Treasurer Rob Lucas said Thursday's industrial action was not going to change his approach.
"It's an absolute nonsense for the union bosses to suggest in any way there's going to be an increase in class sizes or the sorts of things they're talking about," he said.
"We are going to be spending an extra $515 million on schools in the next four years."
Mr Lucas said that funding was guaranteed for learning programs, such as languages, and was separate to spending on classrooms and infrastructure.
"If the union bosses think going on strike is going to change the attitude of me as a minister or the Government, they're sadly misguided," he said.
The union insisted more funding was needed for students with special learning needs, or new arrivals to Australia.
"(The Government) want greater flexibility in the deployment of resources, which can only spell insecurity in that funding into the future," Mr Spreadbury said.
Last week Mr Spreadbury warned parents to "plan now" for schools to be closed this week.
"In terms of any inconvenience, I think parents need to understand one half-day of inconvenience is far outweighed by a lack of funding to their students," he said.
The State Government is also facing industrial action from prison officers concerned about plans to privatise the Adelaide Remand Centre.
Public school teachers last went on strike in 2008, demanding a 21 per cent pay rise over three years.
