'Catholic teachers' demands unaffordable'

The Catholic Education Office in South Australia has warned teachers planning to strike over work conditions that improvements "don't come out of thin air".

Catholic Education says every concession or change has a cost and the current demands from teachers remain unaffordable.

Despite agreeing to a new pay deal of a 2.5 per cent annual increase over the next three years, up to 500 Catholic school teachers plan to walk off the job and rally on Thursday in support of a claim for reduced workloads.

They want a cut in student contact time of 1.5 hours each week, to bring them into line with public sector teachers.

The Independent Education Union says it has been disappointed by a lack of meaningful engagement over the outstanding issues.

Catholic Education director Helen O'Brien says her office is negotiating in good faith.

We've committed to reducing workload and increasing salaries, and we're ready to pay," she said.

"Ideally we would reach agreement without industrial action, but we acknowledge the right of our staff to participate," she said.

Assistant director Michael Kenny said Catholic Education believed it had offered some generous concessions but the union claim was simply unaffordable.

"Changes to working conditions don't come out of thin air. Every concession or change has a cost," he said.

Thursday's strike action is not expected to force schools to close.