Local schools, including Nowra High School, Shoalhaven High School, will be providing "minimal supervision" for students on the day.

Read more: Shoalhaven teachers demand better pay and more sustainable workload

"Students will not be completing their normal classroom lessons and content," Principal of Nowra High School, Glen Kingsley, said in a statement.

"Students who are in attendance on Tuesday will be supervised in collapsed classes undertaking educational activities, however they will not be completing their normal lessons or classroom activities," said Executive Principal of Shoalhaven High School, Damian Rees.

Parents are being reminded to make alternative arrangements for their children, with the majority of schools closing the gates during the strike.

The strike comes after local teachers protested their working conditions last month.

According to the NSW Teacher's Association, 43 per cent of the schools in the Shoalhaven and Southern Highlands had vacant permanent teaching positions in October and there was 50 unfilled positions in total.

Henry Rajendra, deputy president of the association who attended the Nowra rally, said these numbers are "not good enough" and poor work conditions are deterring people from the profession.

"Every school should be guaranteed and assured their full staffing that all their baseline staffing and that's not the case," he said.

"And the reason being is that the profession is not as attractive as it once was. And the fundamental issues are to do with salary."

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Teachers Federation president Angelo Gavrielatos says the "strike will proceed".

"The teacher shortages are too large and their cause, uncompetitive salaries and unmanageable workloads, too great for teachers and principals not to proceed with this action," he said in a statement on Tuesday.

NSW is facing "a large and growing shortage of teachers", he said.

The strike will be the first 24-hour stoppage by teachers in a decade.

The union is also stepping up a statewide advertising campaign focused on the failure of the government to address teacher shortages.

Premier Dominic Perrottet said last week he was disappointed about the plan to strike, saying the 2.5 per cent pay rise offer was "fair and reasonable" in circumstances where hundreds of thousands of people across the state had lost their jobs.

The award that determines the salaries and conditions of teachers expires next month.

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