Risking penalties for defying a New South Wales Industrial Relations Commission (NSW IRC) order, about 50,000 state teachers struck on Wednesday to protest new education policies.

The job walk-off affected about 2,000 state schools. However, a day before the industrial action, the tutors advised parents to keep their children at home.

Although the Federation of Parents and Citizens Association said it sympathised with the concerns of the teachers, it does not support the industrial action because of its impact on the children's learning.

It is the fifth strike to hit NSW since the coalition held the reins of government in March 2011. The IRC could fine the NSW Teachers Federation $10,000 for defying its order not to strike.

NSW Premier Barry O'Farrell urged the IRC to fine the teachers, but Justice Roger Boland, the president of IRC, said the commission would not be influenced by the premier's statement. NSW Education Minister Adrian Piccoli attributed the boldness of the teachers to initiate industrial action to the low fines that the IRC imposed in the past, at less than $20,000.

"The union sees that as a small price to pay for the massive inconvenience that they caused right across the state as a result of the industrial action," ABC quoted Mr Piccoli.

He said the union is against the reform which grants principals more power over the school budget and hiring because the changes threaten union power.

However, defiance was also two-way since some schools opened despite the union action. The Herald Sun reported that the Neutral Bay Public School on the lower north shore in Sydney opened and classes were going on.

Maurie Mulheron, president of the union, said the 24-hour strike may extend until the NSW government listens to their demands.

"We will commit to this campaign for as long as it takes. This is not something that we are going to walk away from.... What the government is intending to do is getting rid of staff entitlements for schools and just using a bucket of money as the determinant for staffing schools,"

Of the 50,000 teachers who walked off their jobs, about 6,000 went to Sydney Town Hall to air their opposition to the reforms and vote on the possible extension of the strike.