Schools across England will be shut down from Friday until further notice as the coronavirus crisis deteriorates, the government has announced.

The move was unveiled by education secretary Gavin Williamson where Friday will be the last day of normal lessons.

However, powers in emergency legislation – to be passed by the Commons within days – will allow ministers to force some schools to remain open, for the children of essential workers.

It means some youngsters will go to different schools, if their own has been shut down, relieving their parents of childcare responsibilities if they are needed to fight the outbreak.

At a Downing Street conference Boris Johnson said schools would not be shut for children of those in crucial jobs such as police officers, delivery drivers and medical staff, but it is not yet clear how this exception will be implemented. The Prime Minister said the Government would ask nurseries and private schools to comply with the measure, which will see exams cancelled for this academic year. Westminster’s top scientific adviser Sir Patrick Vallance said the decision was not being taken because Covid-19 is dangerous to children, but because it is an extra step to stop more at-risk people being infected.

He stressed that mums and dads should avoid leaving their children at home with older relatives ‘who may be particularly vulnerable’. The Government vows to provide financial support to families with children on free school meals who may face extra costs as a result of the move, but concerns remain about how parents who have to go to work will be able to handle the change.

Speaking to colleagues in the Commons today Williamson said: ‘I want to provide parents, students and staff with the certainty they need. After schools shut their gates on Friday afternoon they will remain closed until further notice. This will be for all children except to those of key workers and where children who are most vulnerable.’ ‘I know the situation has become increasingly challenging. I’ve said before that if the science and the advice changed, such that keeping schools open would no longer be in the best interest of children and teachers, that we would act – we are now at that stage.

‘The spike of the virus is increasing at a faster pace than anticipated and it is crucial that we continue to consider the right measures to arrest this increase and to relieve the pressure on the health system.

‘The public health benefits of schools remaining open as normal are shifting. It is also clear that schools are increasingly finding it more difficult to continue as normal as illness and self-isolation impacts on staffing levels and pupil attendance. ‘The scientific advice shows that these settings are safe for this small number of children to continue attending. But asking others to stay away will just go towards helping us slow the spread of this virus.

‘My department is working closely with local authorities, representatives of early years schools and headteachers, regional schools, commissioners and bodies such as Ofsted and Ofqual about how to deliver this change as effectively as possible. ‘And we will do whatever is necessary to support local authorities, schools and teachers through the weeks and months ahead.’