Schools are to close across Northern Ireland from Monday in a bid to delay the spread of coronavirus.
And officials said they could be shuttered until this summer.
Stormont First Minister Arlene Foster said “The societal and economic impact of this measure will be enormous.”
She said the closures were “unplanned and long-term”.
“This is unprecedented,” she added.
“Today I stand here before you not only as Joint Head of Government, but also as a daughter, mother, a sister & an aunt— Michelle O’Neill (@moneillsf) March 18, 2020
“I want to speak to #COVID19 concern within every city, townland & village
“There is only one priority at this time & that is to save lives & to mind people” pic.twitter.com/CDjfyu1uVv
Ms Foster and Deputy First Minister Michelle O’Neill made the announcement in Belfast.
They had been at loggerheads after the Sinn Fein leader wanted to act sooner following a similar move from the Irish Republic.
The five main teaching unions have written to Stormont Education Minister Peter Weir asking him to set a date for closures.
In Ireland, schools have been closed since Friday.
Schools across the UK are to close to all pupils except those of key workers, as Boris Johnson urged the public to continue heeding health advice to help slow the spread of Covid-19.
Mr Johnson said schools in England will close their gates on Friday until further notice, but urged parents not to leave children in the care of grandparents or older relatives who are at higher risk of becoming seriously ill with coronavirus.
He said meals and vouchers would be provided for pupils who currently receive free school lunches, but said “exams will not take place as planned in May and June”.
The move comes as the Welsh Government said all schools will close for an early Easter break by Friday at the latest, just minutes before First Minister Nicola Sturgeon announced schools in Scotland will also close by the end of the week.
Schools in Northern Ireland will close with immediate effect, although teachers will attend for a further two days.
To date, 104 people have died after testing positive for coronavirus in the UK.