Britain has resisted following many European countries and closing schools due to coronavirus, but many parents are defying official advice and keeping their children home.

"I'm not sending them largely because I'm worrying," said Margot, a 45-year-old mother of two daughters, aged six and 10, in Hampshire, the worst-hit county in Britain for cases.

"I just want them to be safe and I want to keep people around me safe," she added.

Prime Minister Boris Johnson on Monday stepped up his government's response to an accelerating outbreak of coronavirus.

He called for household isolation, home-working and an end to mass gatherings, but stopped short of ordering the closure of schools.

Only a handful have shut after confirming cases among staff or students, and Johnson said a widespread closure would have little impact on stemming transmission.

The approach contrasts with that of many other countries, such as neighbouring France where a shutdown of all schools and universities began on Monday.

Some parents are calling the British move too timid.

Olivier, 37, of northwest London, told AFP he does not understand the reasoning of the government "when all the experts and doctors hammer the message of staying at home".

The French businessman's five-year-old daughter could still attend her school, managed by English authorities, while the French-run school attended by his son closed this week.

But the long-time London resident is keeping both at home. 

"I don't think I panicked, I just hope I'm as responsible as possible," he said, adding he believed the government was prioritising "the economic dimension".

'Chaos and confusion' 

An inner city London headteacher, who asked to remain anonymous, reported attendance on Monday of about 90 percent but said by Tuesday that had dropped to "below 70". 

"The problem is we don't know who has got it," he added. "Some families are self-isolating, but nobody is getting tested."

Britain has largely only been testing those showing severe symptoms seeking treatment, despite the World Health Organization urging countries to "test, test, test".

A petition started on parliament's website, calling on the government to "close schools/colleges down for an appropriate amount of time amidst COVID19", had garnered nearly 650,000 by Tuesday afternoon. 

In a letter to Johnson sent Saturday, the National Education Union called on him to publish the modelling and other scientific evidence providing the basis for keeping schools open.

Another union representing teachers and head teachers criticised "the lack of clear information".

The NASUWT said the crisis was "causing chaos and confusion and placing intolerable pressure on all staff in schools and their families."

According to The Guardian, a study reviewed by the government put the cost of closing schools for four weeks at three percent of Britain's gross dometic product.

Candice Edery, a 44-year-old press officer, who has been keeping her two children at home for a few days, is among those defying the government's current advice.

"It seemed to me wiser not to send the children to school," she said. 

"This absence is not really allowed, but frankly I don't care. It's not worth taking risks." 

Meanwhile, Lisa Romano, an Italian living in south London, saw parallels between the cautious British response and how her native country, now besieged by the virus, initially reacted.

"Honestly, at the moment, I'm not feeling very protected by this government," said Romano, who is keeping home her two children - aged eight and 12 - who suffer from conditions including allergies, asthma and epilepsy.

"It's funny, but I would prefer to be in Italy - if you get symptoms there, you get tested. But here they don't. I'm feeling very very stressed."