Glenn Lowe, Independent Education Union delegate and teacher at St Josephs Catholic High School Albion Park said each day was fraught with uncertainty.

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"The deliberate ignorance for 10 years is causing us uncertainty," he said. "We don't know what's going to happen, we don't know how many staff we're going to have day to day."

Mr Lowe and his colleagues are ramping up the pressure on their employer, the Catholic Education Diocese of Wollongong, as part of a state-wide campaign by Catholic school teachers for better pay and action to address teacher shortages.

At his school, Mr Lowe said classes are bundled together as there are not enough teachers for the growing student body.

"They're not getting the delivery they should get, and the biggest concern is we don't know how long it's going to be before it gets resolved."

Mr Lowe's experiences are not unique, Independent Education Union NSW/ACT branch secretary Mark Northam had been hearing similar stories across the state.

"At high school you'll have students in school halls, drama rooms, at worst out in the yard, and you'll have teachers supervising more than one class," he said.

"That's not education, that's supervision."

Employer groups have acknowledged the stress their staff are under. A submission from Catholic Schools NSW, which covers the nearly 600 Catholic schools around the state, forecast a workforce shortage of 15 per cent by 2030, with regional and rural schools the worst affected.

On current teacher numbers, a 15 per cent shortage would be equivalent to 4050 unfilled places.

A Catholic Education Diocese of Wollongong (CEDoW) spokesperson said the organisation prioritised continuity for students with in person instruction.

"As part of our evolving Workforce Strategy we have implemented a range of initiatives to attract and retain high quality, professional teachers and school support staff. Some of these initiatives include our Step Into Teaching Program, providing financial and professional support for Year 12 students to undertake tertiary study in teaching with guaranteed placements on completion; tailored support for our early career teachers; and a wide range of personal and professional development opportunities for all our staff."

The Catholic Schools NSW submission highlights that fewer teachers are graduating into the workforce and a large proportion of the current workforce is reaching retirement age.

To counter this, Mr Northam said Dioceses would need to increase pay and reduce crippling workloads.

Support staff in particular would need to be paid equivalent to their counterparts in the public sector, Mr Northam said currently there is a 10 per cent disparity between the Catholic and public sector for this role.

The CEDoW spokesperson said staff were paid in line with their public sector counterparts.

"It is custom and practice that CEDoW remunerates our teachers with rates of pay that match those of teachers in NSW Government schools."

In a trial, the Broken Bay Diocese, which covers the northern suburbs of Sydney and the Central Coast, will pay teachers above the award rate and allocate an additional hour of preparation time, something that Mr Northam said could be rolled out across the state.

"There's change afoot, but we've got to get the 11 Catholic dioceses to come on board and put an offer on the table and get schools back functioning the way they should be," he said.

"Catholic systemic schools are great schools, they're great places to work when they're staffed properly. And that can be fixed up, but there's no quick fix here."

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