All schools across England will close from Friday afternoon to help authorities tackle the spread of the coronavirus, the government announced on Wednesday (March 18).

Speaking at a press conference at Number 10 Downing Street, Prime Minister Boris Johnson urged the public to heed government advice on social distancing and avoiding unnecessary travel as he revealed schools would close their doors across England on Friday (March 20).

He followed a statement from Education Secretary Gavin Williamson who moments before told MPs that schools would shut indefinitely after lessons had finished on Friday afternoon.

"After schools shut their gates on Friday afternoon they will remain closed until further notice," Williamson said.

"This will be for all children except to those of key workers and where children who are most vulnerable."

He continued: "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."

Addressing the Downing Street press conference, Johnson said "exams will not take place as planned in May and June" after the school closures were announced.

He insisted pupils would still be able to get the qualifications they needed but did not yet offer specifics on how.

The Welsh government said on Wednesday that all schools will close for an early Easter break by Friday at the latest, while First Minister Nicola Sturgeon announced schools in Scotland will also close by the end of the week.

Responding to the announcement, Paul Whiteman, general secretary of school leaders' union NAHT, said the country faces a "truly unprecedented and grave situation".

He said: "Today's decision is a vote of confidence in how schools have responded so far. Schools can be confident they are doing a good job.

"Now, they should also be entitled to expect the necessary support from other organisations with civic responsibilities.

"Whilst NAHT and its school leader members stand ready to assist with this response, there are many complicated issues to address immediately as a result of the government's announcement today.

"This will be our focus in the next few days, to assist our members with this enormous task and to work alongside the Department of Education to make this work on the ground.

"It will not be easy, but the scale of the crisis means that many solutions will have to be tried even though they are less than perfect."