When schools shut in Northern Ireland over coronavirus it will be for at least 16 weeks, Arlene Foster has said.
The first minister was speaking after a meeting between senior ministers from the NI Executive and Irish government.
Two primary schools have said they will close voluntarily, the first primary schools in NI to do so.
The two are Lurgan Model Primary School, in County Armagh, and St Scire's in Trillick, County Tyrone.
Lurgan Model said it would close for the week, while St Scire's will close on Monday ahead of planned St Patrick's closures on Tuesday and Wednesday.
Five new cases of coronavirus have been confirmed in NI while a second person has died in the Republic of Ireland.
There have been 129 confirmed cases in the Republic of Ireland while coronavirus deaths have doubled in 24 hours in the UK.
The first and deputy first ministers met counterparts include Taoiseach (Irish prime minister) Leo Varadkar in Armagh on Saturday.
Speaking after the meeting, Mrs Foster and Deputy First Minister Michelle O'Neill were both still split over the issue of school closures.
Deputy First Minister Michelle O'Neill repeated her call for them to be shut immediately, in line with the Republic of Ireland.
Meanwhile, in a statement on social media, Lurgan Model Primary School said it remain closed all this week.
The school said it was already due to be shut on Monday and Tuesday due to St Patrick's Day and will bring planned closures due for May forward to this week.
It is the first school in Northern Ireland to close voluntarily over the outbreak.
The school said it "will not officially reopen until Monday, 23 March" but will "monitor the situation of this incoming week".
St Scire's, in Trillick, said the school would stay closed on Monday ahead of planned closures on Tuesday and Wednesday for St Patrick's Day. It added that the situation will be reviewed prior to Thursday.
Ministers still divided over schools
Speaking after the meeting in Armagh, Mrs Foster said that schools will close "when we are advised on the medical evidence".
"Children will be at home for quite a considerable period of time, given that when we do close the schools they will be closed for at least 16 weeks.
"Then of course you are into the summer period, so they will be off school for a very long time."
Ms O'Neill said all parties in the executive agreed schools would have to close but it was a matter of timing.
She said: "In my opinion schools should close now. I think we need to be consistent across this island
"I think the fact that you can have two schools a mile apart and one school's open and one school's closed that's a very confusing picture and a very confusing message for the public."
Ms O'Neill first called for schools to close immediately on Friday, a day after she, along with First Minister Arlene Foster, said the executive did not believe the situation had reached that stage.
On Saturday, SDLP leader Colum Eastwood also called for schools to close, after Archibishop Eamon Martin, the leader of the Catholic Church in Ireland, wrote to NI's education minister to ask him to consider closures.
Taoiseach explains closures short notice
However, Taoiseach (Irish prime minister) Leo Varadkar said the main differences between the two governments was over timing.
He said the Northern Ireland Executive and Irish government shared the same objective in slowing the advance of coronavirus but it was inevitable there would be differences in how they approached it.
He added: "But the differences that exist are mostly around timing.
"What there isn't any difference about is our common objective, which is to slow down this virus in its tracks and push it back as much as possible and limit the harm to human health and human life."
Mrs Foster said both governments had "very coherent messages".
Mr Varadkar also explained that the short notice of Irish school closures given to counterparts in Northern Ireland and the UK was "not how we intended it to happen".
"I absolutely guarantee you I did not intend to make that announcement or speak to Irish people on the steps of Blair House in Washington DC," he said.
"We had a plan in place to move to delay phase. We had to bring that forward almost overnight."
He added that Irish officials gave "as many people a heads up as we could, including authorities here in Northern Ireland" but it was also "important that the Irish people should hear the news first from me and from the government".
"That's why the notice that we gave people here and elsewhere was so short but there was no perfect way of doing this unfortunately and I appreciate the understanding of the first minister and deputy first minister," he added.
Health Minister Robin Swann, Tánaiste (Irish deputy prime minister) Simon Coveney and Irish Health Minister Simon Harris also attended the meeting.
Sinn Féin president Mary Lou McDonald - who was not at the meeting - said the UK's response to coronavirus "should be rejected" and is "totally unacceptable in the north of Ireland".