The first minister has said schools and nurseries across Scotland will close from the end of this week and may not reopen before the summer.
Nicola Sturgeon announced the move as it was confirmed a third patient in Scotland has died after testing positive for Covid-19.
The total number of coronavirus cases is now 227, up 32 on Tuesday.
Ms Sturgeon said: "My view is that it is now inevitable that we will close schools and nurseries.
"My planning assumption is that schools will close to pupils at the end of this week. I wanted today to give parents notice of that."
The first minister said the decision was driven by two key factors.
She added: "First is the science. I expect that is likely to tell us to close schools.
"Secondly, schools are reaching the point where they have lost too many staff to continue."
Ms Sturgeon said Education Secretary John Swinney would set out arrangements on Thursday and address questions about exams and what it meant for key workers.
Schools and nurseries will close from this Friday @NicolaSturgeon announces. I appreciate this will be very disruptive but it is necessary. We are working with Councils to support young people preparing for @sqanews exams, are vulnerable and whose parents are essential workers.— John Swinney (@JohnSwinney) March 18, 2020
She said: "We are still working out the fine detail of what exactly this will mean."
Ms Sturgeon added: "The clearest guidance I can give is that schools and nurseries will not reopen after the Easter break.
"At this stage I cannot promise that they will reopen before the summer holidays."
The first minister said: "People's way of life will be changing dramatically, and potentially for some time to come.
"Lives are being disrupted like never before."
Education secretary John Swinney said the advice from the scientific community suggests the closure of schools would assist with "flattening the curve".
Mr Swinney also said the move would help suppress the rise in cases.
He told BBC Radio Scotland's Drivetime: "It is becoming increasingly difficult to sustain education."
Staff and pupil absences have soared in recent days and some schools have been closed for deep cleaning.
Mr Swinney also described closing schools and nurseries as "perhaps the most difficult decision we have had to come to so far" during the outbreak.
He added: "We recognise this will be very disruptive to members of the public."
The focus will now switch to digital learning and Glow, the Scottish schools national intranet.
Mr Swinney added: "We are in really quite exceptional times and we have to take realistic and pragmatic decisions."
The education secretary said one of the key issues that still has to be finalised is how children of essential workers, like NHS staff, are looked after while they are at work.
But Mr Swinney said although schools would be closed, there would be "an element of continuation of delivery of service".
He said there were three options for the spring's SQA exam diet:
- It goes ahead as planned
- It is re-scheduled for a later date
- Or an "alternative certification mechanism" is introduced which would be based on a variety of different pieces of work and teacher feedback.
More details will be announced in the Scottish Parliament on Thursday.
The Scottish Qualifications Authority described the school closures as "a very serious and evolving situation".
A spokesman said: "Every effort should be made to ensure schools remain partially open to allow senior phase pupils to complete learning and be able to submit coursework, in addition to being able to open as examination centres during the diet, should medical and scientific advice allow.
"As you would expect, the SQA is working through a range of scenarios, including in the event that there is significant disruption to the diet.
"In the meantime, we strongly suggest that schools and colleges continue to prioritise the completion of coursework, including for those subjects with later deadlines."