Closing schools across New South Wales could increase the spread of coronavirus by putting students out into the community in a more widespread manner, the secretary of the NSW Department of Education, Mark Scott, says.

Key points: The NSW Department of Education will be sending coronavirus advice to schools this weekend

The NSW Department of Education will be sending coronavirus advice to schools this weekend Four schools in the state have been shut following confirmed cases

Four schools in the state have been shut following confirmed cases Schools will advised to consider tactics such as staggering recess and lunch breaks

The department will be sending advice to schools over the weekend about managing the outbreak, but Mr Scott said the mass closure of schools was not necessarily something that would stem the growth of infections.

"If you just shut the schools, the kids are all down at the shopping centre or at the playground or at the movies, or perhaps being minded by grandparents or others — that may not actually be helping to limit the speed of the spread of the virus in the community," he said.

There are more than a million students in the government and non-government sectors.

"At the moment the advice from New South Wales Health is that we need to be managing this well within the school context, but to keep the schools open," he said.

Schools will be asked to consider strategies such as staggering recess and lunch breaks, and decide whether meetings should go ahead.

Mr Scott said the most important advice for parents was to keep sick children at home.

"If your child has a heavy cold, cough, fever, and respiratory, flu-like symptoms, then this is not the time to solider on," he said.

"Many a parent has looked at a child who's been a little bit marginal … and they've said come on, off you go … this is not the time for that now."

The Australian Primary Principals Association said there was concern that teachers and school leaders aged over 50 could be more at risk than students during the outbreak.

Contingency plans are being developed, in case teachers become ill and are unable to return to work.

The association's president, Malcolm Elliott, said it was a complex issue to tackle.

"Most schools leaders are aged 50 or older and if we have a virus that's going to affect older people and if this was to lead to widespread illness among teachers and school leaders, then we need other people to replace them in their schools," he said.

Katoomba High School in the Blue Mountains was closed for the day on Friday after a confirmed coronavirus case, making it the fourth school in the state to face a lockdown over the virus.

NSW yesterday reported its biggest daily jump with 14 new cases, bringing the total of confirmed cases to 92.

It comes as the Sydney Royal Easter Show has been cancelled after Prime Minister Scott Morrison announced the cancellation of non-essential mass gatherings of more than 500 people from Monday.

The show was due to begin on April 3, with more than 800,000 people expected to attend the 12-day event.