Independent Education Union Australia NSW/ACT branch Newcastle organiser Therese Fitzgibbon said members at all 58 Diocese of Maitland-Newcastle schools had unanimously moved a motion to be included in an application to the Fair Work Commission for a protected action ballot order.

She said any action is likely to be a full day strike.

"It's the holidays and teachers will be recovering from burnout as a result of a term that consisted of significant staff shortages, both anticipated and not anticipated as a result of COVID... and doing a lot of the paperwork they should have been doing during term but they wouldn't have been able to get to," she said.

Ms Fitzgibbon said the diocese had indicated it would match the Department of Education's offer to public school teachers, but this was limited by the state government's 2.5 per cent cap on public servants' pay rises.

She said IEU members were calling for a 15 per cent pay rise over two years and an extra two hours of preparation time each week.

She said non-competitive salaries and unsustainable workloads were contributing to staff shortages and COVID-19 had exacerbated the issue.

"What you're hearing consistently is teachers coming to work sick - not with COVID but with other illnesses - because they know there is no-one to replace them, that there is just a complete and utter absence of teachers out there," she said.

Teachers were teaching multiple classes at once, she said, schools were splitting classes and principals and executive staff were teaching.

She said even specialist staff supporting students with special needs, Indigenous students and students with English as a second language were being put onto class.

"They're genuinely distressed - they've taken those roles because they want to support those students. The kids aren't getting that support because they're teaching year five because the year five teacher is sick."

Director of Schools Gerard Mowbray said the diocese "fully respect the rights of our employees to take industrial action but the prospect of further disruption on the back of the challenges of the last two years is disappointing".

He said teachers and support staff deserved a "meaningful increase in pay and conditions" and the diocese had "made commitments around increased pay and better conditions and are negotiating productively with the union to agree other measures".

He said the diocese gave staff an extra professional development day this year and to combat the teacher shortage had a "variety of strategies" that had this year attracted about 100 staff from outside the diocese.