New South Wales public school teachers have stopped work for two hours this morning over State Government moves to give schools greater control of budgets and staffing.

By striking, the teachers are defying a direction from the State Industrial Commission.

About 750,000 students are affected by the action, which began at 9am (AEST).

Teachers Federation president Maurie Mulheron has described the government's reforms as a 'wolf in sheep's clothing', designed to reduce job security and increase class sizes.

He has defended the decision to stop work within school hours.

"We've been meeting after school now for weeks," he said.

"We've met after school on many occasions. We've been meeting on the weekend, we've been putting to the Government for months, 'why aren't you including the profession in this?'

"In fact it was an ambush on the profession, there's been a secret steering committee that the Department has had since last August."

The Government and the Teachers Union have accused each other of deliberately spreading misinformation about the changes.

The Education Minister Adrian Piccolli says the union has been misleading its members about the reforms and how much the union's been involved in consultation.

"In terms of the policy detail, the union's very much involved," he said.

"They oppose these reforms because it means that individual schools have a greater say in how those schools are run and it removes a lot of the decision making away from the central bureaucracy.

"Unions see that as a threat to their power and that's why they're opposing these reforms."

On Wednesday, the Industrial Relations Commission recommended the Teachers Federation be given a seat on the Steering Committee overseeing the reforms.

However Mr Piccolli says that is a decision for the Education Department's Director-General.

New South Wales' P&C Federation spokeswoman Rachel Sowden says the group does not support the teachers' action, but it is an understandable step.

"P&C Federation doesn't support strike action because it does impact on our kids' learning time, but we do understand why the teachers federation felt it needed to do this strike today," she said.

Ms Sowden has described it as an unwelcome disruption.

"What we would have hoped was that it didn't come to this and we would always ask that the stakeholders sit down and talk," she said.

"Obviously there will be parents who are upset by this action."

Parents have been asked to contact their children's school for specific details.