Thousands of public school teachers have marched through the Sydney CBD as part of their 24-hour industrial action over wages and conditions.
The strike action is in defiance of a NSW government plea to wait until after next month's budget to solve the pay dispute.
It is the second walkout in six months.
Earlier this week, Premier Dominic Perrottet and Education Minister Sarah Mitchell said wage negotiations would be delayed until after the budget.
NSW's public service has a legislated 2.5 per cent cap on wage increases.
Ms Mitchell said the government planned to address wage increases across the entire public sector in the upcoming state budget.
"But they're big decisions, it's billions of dollars that government needs to decide about how we're going to spend this money," she said.
"That has to happen as part of a budget process and I think taxpayers would expect us to do that."
Teachers waving banners such as: "we strike for our students", gathered in their thousands outside state parliament.
Teacher Nancy Penfold from Marrickville Public School in Sydney's inner west told the crowd, teachers wanted to improve conditions for students around the state.
"Kids deserve qualified teachers in every classroom. Teachers [deserve] better working conditions and a competitive salary that will attract and retain the teachers we need," she said.
Uralla Central School Principal Michael Rathborne from the NSW New England has been a teacher for 30 years and said he had never seen things so bad.
"Things have never been worse, when it comes to staffing our schools," he said.
"Both my deputy and I now far too regularly take classes to avoid minimal supervision, we do that to help our staff because the burden is too large there."
Teacher's Federation president Angelo Gavrielatos said the government has had enough time to resolve the dispute.
"We've been very patient, the government must act," he said.
A union survey of 10,000 members found seven in 10 teachers believe their workload is unsustainable.
Ms Mitchell rejected an assertion that the only way for teachers to get an increase was to go on strike.
"We've had pay increases of 2.5 per cent year-on-year for our teachers," she said.
"We put one in in January this year even though we hadn't yet landed the award because we knew that that's what teachers were entitled to under our wages policy, so we've done that regardless fo the industrial issues."
"We want to get a fair and reasonable outcome here and we are looking at these issues for all of our frontline staff here in NSW."
Ms Mitchell said $125 million had been allocated in last year's budget to grow the state's teaching workforce and attract new people to the profession.
In Dubbo, about 300 teachers and supporters from across the NSW Western Region marched down Talbragar Street as part of the statewide strike.
Dubbo teacher Braydon Holland said the state would need close to 15,000 teachers over the next decade to meet demand.
"My school will be seeing at least 6,000 classes disrupted if not outright cancelled by the end of this year — the kids in Dubbo are the ones suffering," he said.
"Our record was 285 students on single minimal supervision, that is two teachers and a teacher supervisor, for nearly 300 kids — that level of staff is unacceptable."
The Teacher's Federation estimates more than 2,000 teachers attended a rally in Coffs Harbour on the state's Mid North Coast.
Schools throughout the region were represented, with some coming from as far as Port Macquarie.
Belinda Mellalieu said she had recently taken leave without pay from the school where she teaches in Bellingen to pursue a career change.
"I'm classified now I think as a statistic — I've been teaching for 25 years, and this last five years have been the hardest and toughest I've ever experienced," she said.
"It's not because of the money, it's because of the workload – it's because of the lack of support we're getting from the (Education) department to help us help these children."
Schools remained open but with minimal supervision and no classes.
