The start of the school term in January has been delayed by the Welsh Government to give schools a chance to plan for the return of pupils and a potential move back to remote learning in the event of an expected coronavirus surge.
This comes as concerns continue to mount over the Omicron Covid variant and a large increase of cases in the coming weeks.
Education Minister Jeremy Miles has written to schools telling them to plan for teaching to go back online should a "very high risk" situation emerge in the new year.
He said: "I am providing all schools with two planning days at the start of the spring term.
"This will allow time for schools to assess staffing capacity and put the necessary measures in place to support the return of all learners.
"Schools will be asked to make use of the planning days to ensure they have robust plans in place to move to remote learning if required – this could be for individual classes/year groups or possibly for the whole school.
"Schools will be asked also to use this opportunity to revisit contingency plans, ensuring exam years are prioritised for onsite provision should there be a need to restrict in person learning at any time and consider what arrangements might need to be in place for vulnerable learners and the children of critical workers during any periods of disruption."
Mr Miles also confirmed he was issuing a Coronavirus Act 2020 Notice to allow schools to operate staggered start and finish times from the start of the new term.
Schools in Denbighshire and Anglesey have already confirmed classes will move online from next week in a bid to curb transmission in the lead up to the holidays.
Ministers are meeting to review Covid restrictions on Thursday with an announcement expected to be delivered on Friday.
Mr Miles said the priority "continues to be to minimise the disruption to education, and ensure where possible learners continue to receive in-person learning, as well as protecting school staff and learners".
He added: "I am providing all schools with two planning days at the start of the new spring term, this will allow you time to assess staffing capacity and put the necessary measures in place to support the return of learners."
Headteachers union NAHT Cymru welcomed the announcement from the Education Minister.
Laura Doel, of head teachers' union NAHT Cymru, said: "Schools have suffered significantly from staff absence since September and, given that the new variant is even more transmissible, we can be certain that Covid will continue to impact on staffing levels.
"School settings cannot stay open and remote learning cannot be supported if the workforce is unavailable, that is why we urge the Welsh government to introduce additional mitigation measures, like staggering session times to control the flow of learners and parents coming in and out of school, at the start of next term."
However, the Welsh conservatives say that keeping schools open should be a priority.
Laura Anne Jones who is Shadow Education Minister said: “The youngest in our society have sacrificed so much during the pandemic to protect others at a huge cost to their own life chances.
“Therefore, it is essential we do everything we can to ensure schools are kept open at their normal capacity.
“Education is not expendable, especially for vulnerable children where their time away from home is their only respite from abuse.
“There are legitimate concerns over workforce availability if a significant wave hits the country, and that’s why the priority and energy of government must be directed at rolling out the booster jab programme as quickly as possible.”
Sally Holland, the Children's Commissioner for Wales told ITV Wales: “I think today's announcement is a proportionate response to a very fast-moving picture.
"It gives school leaders, who have worked so hard against the odds to provide a safe and nurturing education environment for our children, the time and space in the new year to take stock of the availability of staff and properly assess the situation.
"Critically for me, it should mean children and young people beginning the next term with as much clarity as the circumstances allow, limiting as much as possible the huge impact the virus continues to have on their learning and their wellbeing.
"I acknowledge that if the new term was to restart without the time to do this, it's possible that there would be greater disruption for children and their families.
“Throughout the autumn term, there have been considerable concerns about supporting young people sitting exams. "I'm pleased to see further support announced today in response to this ongoing and significant disruption – it’s critical that pupils know that they have options and support, and that this package of support is delivered to them without delay.
“There are few straightforward solutions but I continue to press the Education Minister and his team to consider the wide range of children’s needs and rights as they make these difficult decisions.”