TENS of thousands of NSW teachers yesterday voted to take further strike action during the HSC period and early next year if the State Government failed to meet salary and staffing demands.

Teachers stopped work for two hours yesterday from 9am, leading up to 300 schools to close and some to offer minimal supervision to students.

The president of the Federation of Parents and Citizens Associations, Dianne Giblin, said many parents would have taken the day off work to care for children.

She said many children in rural and remote areas would have taken the entire day off because their school bus would not have been running later in the day. Those in city areas would have had to pay full bus fares to get to school at 11am because their bus passes were restricted to early morning use.

Mrs Giblin said she was also concerned that year 12 students may be adversely affected by further strikes in October and November, during the Higher School Certificate period.

"We are concerned about the rolling strikes," she said. "It will affect young people's preparation for the HSC, it will add additional stress that young people don't need."

The president of the NSW Teachers Federation, Maree O'Halloran, said HSC students would not be affected by further strikes because teachers were not involved in exam supervision. She said teachers would still make themselves available to HSC students seeking their assistance with exam preparations.

"We wouldn't do anything to disrupt the HSC," she said.

Ms O'Halloran, who is expected to resign from her position later this month, said the majority of about 20,000 teachers voted in favour of taking further strikes from October and January next year if the State Government failed to meet their demands for a 16 per cent pay rise over the next three years.

The NSW Treasury has offered public servants an annual increase of 2.5 per cent.

Teachers are also protesting over changes by the State Government to the teacher transfer system, which they say will disadvantage schools in remote towns and other hard-to-staff areas.

A spokesman for the acting Minister for Education, John Hatzistergos, said about one-third of teachers turned up to work yesterday morning while two-thirds took part in the two-hour Sky Channel meeting.

The Department of Education's director-general, Michael Coutts-Trotter, said 88 per cent of more than 2200 schools in NSW were operating yesterday with at least minimal supervision.

"Parents and children were disrupted over a wage agreement which is in place until the end of the year," Mr Coutts-Trotter said.

"NSW public school teachers are among the highest paid in the country, with salaries ranging from $50,000 for new teachers and $75,000 for experienced educators. The wages for our most experienced classroom teachers have increased by 75 per cent since 1995."

He said teachers received a 4 per cent pay rise in January after increasing by 4.5 per cent a year in 2006 and last year.

It is understood Ms O'Halloran plans to take a new job in welfare rights and that the deputy president, Bob Lipscombe, will replace her as president.