Catholic school staff are backing next week's strike by teachers in NSW public schools and say they could follow suit.
The union representing teachers and staff from Catholic schools endorsed the planned 24-hour strike on Wednesday by the NSW Teachers Federation for improved pay and conditions.
The Independent Education Union of Australia says if it gets the formal support of its members, they will take their own industrial action in May.
The NSW Teachers Federation has also authorised public school teachers to walk out if NSW government MPs arrive on campus and banned the implementation of new government policies or initiatives.
Public school teachers are seeking a pay rise of between five and 7.5 per cent, as well as two extra hours of planning time.
The members made good on their promises on Wednesday, with dozens of teachers walking off grounds after Premier Dominic Perrottet and Education Minister Sarah Mitchell arrived for the school's opening in the Sydney suburb of Meadowbank.
The premier said he was welcomed by school staff despite the walkout.
"Let's be fair dinkum, this is the Labor Party and the union movement playing politics with our kids and our parents," Mr Perrottet said.
He maintained the issue was being resolved, indicating it would be dealt with in the June budget "in a fair and reasonable way".
"We are working through these issues to reach an outcome that we believe is fair and reasonable," he said on Wednesday.
The Independent Education Union said it supported the Teachers Federation and its members, saying teachers had "been pushed to breaking point".
"It's time for meaningful action now," the IEU's secretary for NSW and the ACT, Mark Northam, said on Thursday.
"The sharply rising cost of living, lack of real wages growth, ever-increasing workloads and global pandemic have led to crippling staff shortages.
"Our members are exhausted and burnt out."
The IEU is negotiating an enterprise agreement for 18,000 members in Catholic schools.
Members are calling for a pay rise of 10 to 15 per cent over two years, pay parity for support staff with public sector workers, less paperwork and extra planning time.
The IEU cannot engage in industrial action without a formal ballot of members.
That process was underway and pending the outcome, the union would take its own industrial action in May.
"It's time for a fair deal for teachers and support staff - it's the only way to attract and retain the right people to fix the critical shortages and guarantee teaching and learning for our students now and into the future," Mr Northam said.
