Thousands of NSW teachers will strike on Thursday after the state budget failed to deliver an improved pay offer.
Unions representing public and Catholic school teachers met last Tuesday as the NSW budget was handed down, announcing they would strike for 24 hours on June 30.
"The government has failed students, and continues to fail students and the teaching profession," NSW Teachers Federation president Angelo Gavrielatos said.
Forbes High School and Forbes Public School will be non-operational with no student supervision available on the day, posts to the schools' Facebook pages said.
Forbes North Public School's newsletter said it would remain operational with restricted supervision.
The industrial action comes after the two teachers' unions gave Premier Dominic Perrottet an ultimatum to improve the three per cent pay deal offered over the next financial year.
Tuesday's budget papers revealed no further offer was on the table.
"Every single day teachers and principals have been even more burdened with their workloads, and the stress associated with the teacher shortage.
"This teacher shortage is 10 years in the making."
Independent Education Union NSW/ACT secretary Mark Northam said the government's inaction on teacher shortages had left the Catholic school system in a mess.
Catholic schools in inner city areas like North Sydney and Canberra were struggling to recruit teachers.
"If you're sharing classes, standing in the doorway between classes, having multiple classes in school halls, then teaching and learning has been compromised," he said.
"(Our parents) sons and daughters are telling them what's going on and how they're missing out."
But the premier slammed the scheduled strikes as disappointing and politically mobilised by the unions, referring to his government's proposed pay increases to public sector workers.
The new policy confirmed in the budget on Tuesday includes a three per cent pay rise in each of the next two financial years, with another 0.5 per cent the following financial year for workers who make a "substantial contribution to productivity-enhancing reforms".
This allows a possible increase of 6.5 per cent over the period.
"We are the only state in the country that has pay increases of up to three per cent. These strikes are politically motivated (and).. they're not happening in any other Labor state," Mr Perrottet told 2GB on Tuesday.
"The inconvenience now ... that parents across our state will endure because of the actions of the union movement ... is incredibly disappointing," he said.
"It needs to stop ... it's not like we've frozen wages".
Public sector workers argue the pay increases are not enough and translate to a real wage cut, with inflation running at 5.2 per cent and forecast to tip over seven per cent.
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