Prime Minister Scott Morrison insists schools will remain open — for now — as governments across the country face increasing heat from parents opposed to the decision.

The ABC understands absenteeism — particularly in affluent areas — is as high as 30 per cent as parents struggle to understand why schools should stay open when social distancing is being encouraged elsewhere.

Mr Morrison said he was following the advice of the Government's health experts and young people were a low-risk group.

Closing schools would put pressure on health workers to stay at home to look after children, and hurt the economy more broadly, he said.

"The disruption that would occur from closures [of schools] around this country would be severe.

"Let's keep our heads as parents.

"What do I mean by severe? Tens of thousands of jobs could be lost, if not more," he said.

"The impact on the availability of health workers — a 30 per cent impact on the availability of health workers."

Singapore, China held up as examples

Mr Morrison cited Singapore as a country which had successfully controlled the virus while keeping schools open.

A report from the US Centres for Disease Control and Prevention examined the impact of school closures overseas and found short-term school closures did not affect the spread of the virus.

"Available modelling data indicate that early, short to medium closures do not impact the epi curve of COVID-19 or available health care measures," the report said.

"In other countries, those places who closed school (e.g. Hong Kong) have not had more success in reducing spread than those that did not (e.g. Singapore)."

The report said longer closures of eight to 20 weeks may have some impact on community spread, but other measures such as handwashing and home isolation had a greater effect.

The same report also mentioned the danger of closing schools, saying it could lead to young people having greater contact with at-risk groups.

Australia's chief health officer, Brendan Murphy, said there had also been very few cases of coronavirus diagnosed in children in the Chinese province first affected by the outbreak.

"Only 2.4 per cent of the cases reported in Hubei province were in people under 19," he said.

"Children have very, very few instances of clinical disease and, if they do, of even more severe disease."

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Closing schools 'takes doctors off frontline'

Australia's largest not-for-profit healthcare provider, which runs 80 public and private hospitals, says if schools are closed, they must convert to a childcare service for the children of health care workers.

Catholic Health Australia (CHA) estimates 80 per cent of its staff are women with school-age children.

"Catholic hospitals are willing and able to fight the virus, but our ability to do so will be jeopardised if a large number of nurses and clinical staff are taken off the frontline," said CHA chief executive Pat Garcia.

"One option might be to, where appropriate, provide resources to ensure the children of health workers can remain supervised by staff at school during school hours — and potentially beyond."

Norway and Belgium are two countries that have closed their schools to most students, but insisted they remain open as a childcare service for health workers.

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Some parents should keep kids home: expert

Kamalini Lokuge, from the Australian National University's Research School of Public Health, said people who could take their children out of school should do so, but only if they did not have to leave them with grandparents.

She said this would protect the children of people such as health workers, who needed to send them to school so they could work.

"Our essential workers, our doctors, our nurses, those who supply our food, our electricity — they need to be able to send their kids to school," Dr Lokuge told a panel discussion hosted by the National Press Club.

"And if we reduce the number of kids in school, we reduce what we call the force of infection in schools — so kids are going to have less contact with other kids, and therefore, there's less risk of those kids who do need to be in school passing infection on to their family."

Infectious disease expert Robert Booy, from the University of Sydney, said children were probably contracting coronavirus but it was going unnoticed.

"My suspicion is that they're actually catching it, but they're dealing with it so well, they're having such a mild reaction, that it looks as though they've got only a mild cold or no symptoms at all," Dr Booy said in a video published by the university today.

"Younger children with poor hygiene are most at risk of spreading the virus, but with older children, if they're washing their hands for 20 seconds with soap, the risk is lessened.

"Certainly they could pass it to someone in their family but I don't see them as super spreaders."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 2 minutes 36 seconds 2 m 36 s What did Singapore and Hong Kong do to control coronavirus?

What about teachers?

Teachers who fall into higher-risk categories are having to make tough decisions about isolating from their families.

Others have criticised a lack of hygiene products on school grounds, which makes department guidance on social distancing difficult to carry out.

"Schools have been told to implement a range of social distancing measures, which include keeping a distance of 1.5 metres between persons and minimising physical contact where possible," NSW Teachers Federation president Angelo Gavrielatos said.

"However, the design of many of our schools and the size of our classrooms make this impossible.

"The overcrowding of some schools also makes this impossible beyond the classroom.

"This is further amplified on wet days when children and their teachers have to remain indoors."

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School holidays could be extended

The federal and state governments have been discussing starting the Easter holidays a week early.

The ABC understands plans were well advanced but have been delayed after last night's national cabinet meeting.

A sharp rise in infections could see it back on the table.

Governments believe it is a sensible compromise that will avoid a more drastic shutdown.

The Government has made clear that if schools closed now it would likely be for six months.

In practice, that could mean many students needing to repeat their entire year of schooling.

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Aside from a relatively small number of independent schools, the Catholic, independent and public school sectors had all been in support of keeping schools open.

That changed yesterday when Catholic Schools Sydney — which represents 150 schools —broke ranks and called for school closures.

Since then, others in the sector had done the same.

The ABC understands the Catholic education sector had, behind closed doors, been pushing strongly for its schools to be shut.

That had put extra pressure on government, and has been viewed as unhelpful by other school sectors following government advice.

This afternoon, National Catholic Education Commission executive director Jacinta Collins said Catholic schools would adhere to the Australian Government's advice to remain operational.

"While there is significant concern and debate regarding school closures in Australia to minimise the spread of COVID-19, it is our view that the government and public health authorities are in the best position to determine whether schools should remain open and we will adhere to this advice."

The Prime Minister stressed all the states were unified.

"The health advice here, supported by all the premiers, all the chief ministers and my Government is that schools should remain open," he said.

Professor Murphy said the virus affected children quite differently to influenza and other respiratory diseases, which could be quite severe in children.

He said, however, that it was not known whether children could spread the illness without showing symptoms, so schools needed to be made as safe as possible.

Sick children and teachers should not attend, large assemblies and other gatherings should be limited, and good hand hygiene should be enforced, he said.