The prime minister has announced that GCSEs and A levels will be cancelled this year during the coronavirus outbreak, and that all UK schools would close this Friday.
"Hitherto the advice has been that we should keep schools open if possible, in order to reduce the pressure on the NHS and on all other public services," Boris Johnson said.
He added that the judgement to keep schools open had always been under "constant review" and said "looking at the curve of the disease and looking at where we are now, we think now that we must apply further downward pressure on that upward curve by closing the schools".
He said schools would remain closed from Friday for the "vast majority of pupils until further notice".
Coronavirus shuts down schools
"The objective is to slow the spread of the virus and we judge this the right moment to do that. But, of course, as I've always said, we also need to keep the NHS going and to treat the rising number of cases, so we need health workers – who are also parents – to continue to go to work and we need other critical workers with children to keep doing their jobs, too," he said.
He said police officers, supermarket delivery drivers and care workers for the elderly would all be among critical workers needing further support from schools.
"So we, therefore, need schools to make provision for the children of these key workers who would otherwise be forced to stay home, and they will also need to look after the most vulnerable children," Mr Johnson said.
He said this would mean there were far fewer children in schools, which would help to stem the spread of the virus.
Nurseries and private schools were being asked to do the same, the prime minister said. And he added that there would be provision of vouchers for pupils eligible for free school meals.
"And, of course, this does mean that exams will not take place as planned in May and June, though, of course, we will make sure that pupils get the qualifications they need and deserve for their academic career," Mr Johnson said.
He added that the government will work to protect students' qualifications and future interests "fairly".
In a statement to the House of Commons, education secretary Gavin Williamson said: “I can confirm that we will not go ahead with assessments or exams and that we will not be publishing performance tables for this academic year. We will work with the sector and Ofqual to ensure children get the qualifications that they need.”
Labour’s shadow education secretary Angela Rayner said there was widespread concern about exams.
She added: “Clarity is required about children who were due to sit their Sats, GCSEs and A levels and now will not do so. Can he tell us how decisions will be made and how they will be communicated?”
Mr Williamson responded to say he was working with Ofqual to have a detailed set of measures to ensure every child got the recognition they need for the work they have done towards GCSEs, A levels and other qualifications.