Public school teachers have taken to the streets of Sydney to protest wages and conditions.

In defiance of the NSW government’s plea for teachers to hold off on industrial action until after next month's budget, educators have undertaken the second walkout in six months.

The NSW Government has a legislated 2.5 per cent cap on wage increases for the public service, but Education Minister Sarah Mitchell said the government would address wage increases across the entire public sector in its upcoming 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.”

Thousands of teachers descended on state parliament, where teacher Nancy Penfold told the crowd teachers were striking for students.

“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.

Principal Michael Rathborne said he has not seen things so bad in his 30 years as a teacher.

“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.”

Seventy per cent of teachers in a recent union survey of 10,000 members said their workloads are unsustainable. 

The Education Minister denied that the strike was needed to further their cause. 

“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 of 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 says last year’s state budget included $125 million to grow NSW’s teaching workforce.