The move to close school buildings in Scotland to most pupils until at least the start of February has been welcomed by teaching unions.
As part of the measures to tackle the sharp rise in coronavirus cases, schools will switch to remote learning for most pupils until February 1.
A group representing parents said the measures were necessary but would increase stress on families.
Schools will still be open for the children of key workers who cannot work from home and for vulnerable youngsters.
Teachers had previously raised concerns about virus safety in schools before the new year, with some union branches threatening industrial action disputes with local councils.
Dr Patrick Roach, general secretary of the NASUWT union, said: “We welcome the First Minister’s announcement that schools will remain closed to all but key worker and vulnerable children until at least February 1.
“This will provide a measure of relief to many highly-anxious teachers, parents, pupils and school staff at this difficult time.”
He added: “The First Minister stated that the significant uncertainty on the impact of the new variant on children, along with the overall high level of virus transmission in the community, had guided the decision to extend the period of remote learning.
“It will now be vital that in reviewing the closure of schools on January 18 the minister continues to be guided by the medical and scientific evidence on the impact of the new variant, with the priority the safety, health and welfare of children, young people and school staff.
“The highly cautious and preventative approach set out today must be maintained in order to protect health and welfare.”
Larry Flanagan, general secretary of the EIS union, said: “There was already heightened concern from teachers in Level 4 areas around school safety and the surge in infection levels, driven by the new variant, will have compounded those concerns, especially as it seems clear that children can be as easily infected as anyone by the new strain, with subsequent transmission also occurring.
“Whilst the education system is better prepared to deliver education remotely than during the first lockdown, challenges remain and we need to ensure that all pupils, particularly those from disadvantaged backgrounds, can access learning on an equitable basis.”
The National Parent Forum of Scotland said it was important to ensure parents knew they could ask schools for help.
The forum’s chairwoman Margaret Wilson said: “There is no decision today that is going to please everyone in this situation.
“The pressures faced by families, living with restricted measures, coping with stress created by the pandemic, supporting remote learning whilst balancing many other issues, will be a challenge to all parents/carers.
“Our young people have already been through a significantly stressful time. However, the safety of our children and young people is paramount.
“Most importantly we must ensure parents are aware that their school is available for support and to make contact with them as soon as possible.”