The Welsh Government issued the guidance on Monday evening that where social distancing cannot be maintained face coverings should be worn.
Education minister Jeremy Miles MS confirmed this was now the “national approach”.
“This is a temporary, precautionary measure that will be in place for the remaining weeks of term at which point the position will be reviewed. This should come into effect in all settings as soon as possible,” Mr Miles said.
It reinforces the need for everyone in Wales to get their vaccine or booster when offered, wear face coverings when necessary, and book a test if they develop symptoms
“With three weeks left of term, it is vital that we ensure that learning can continue for as many learners as possible,” he added.
The rule applies to all staff and learners in those settings, the minister said.
Although he noted many schools are already operating on this basis due to their own risk assessments.
Mr Miles said: “The emergence of this new variant is a serious development in the ongoing pandemic.
“We have already taken swift action on international travel, alongside the other UK governments. We are now introducing an additional measure, while we learn more about this new strain.
“There remains a lot we don’t know about this new variant. With this high level of uncertainty, it is right that we remain cautious while prioritising the continuation of education.
“It reinforces the need for everyone in Wales to get their vaccine or booster when offered, wear face coverings when necessary, and book a test if they develop symptoms.”
Mr Miles said he would be writing to all institutions on Wednesday to set out the new guidance.