Thousands of pupils are scheduled to return to school in England after months of home study and remote learning.
All children will be able to return to class from Monday under the first step to ease restrictions, but secondary schools pupils can stagger their return to allow for mass testing.
Secondary school pupils will be asked to take three voluntary Covid-19 tests on site and one at home in the first two weeks, before taking home tests twice weekly.
They are also advised to wear face coverings wherever social distancing cannot be maintained, including in the classroom.
Primary school pupils do not have to take tests are wear face coverings.
Prime Minister Boris Johnson said there were dangers involved in keeping classrooms shut for too long when asked about the risks of schools returning.
He said on Sunday: “I think the risk is actually in not going back to school tomorrow given all the suffering, all the loss of learning we have seen. I do think we are ready, I think people want to go back, they feel it, they feel the need for it.”
Pupils in England, except children of key workers and vulnerable pupils, have been learning remotely since the start of the lockdown in January.
The latest Government figures show that more than one in four (27 per cent) primary school pupils in England were being taught on-site in the week after half-term.
Overall, nearly a fifth (18 per cent) of state school pupils were in class on February 25, up from 16 per cent on the week before half-term, according to the DfE statistics.
In Northern Ireland, the youngest children will also return to primary schools on Monday, but they are set to go back to remote learning after two weeks.
In Scotland, children between the ages of four and eight in primaries one to three returned to school last month, alongside some secondary pupils who needed to do practical work.
All primary school pupils in Scotland are due back in classrooms on March 15, while secondary pupils are likely to receive some in-school education each week before the Easter break.
Children aged between three and seven also started a phased return to school in Wales on February 22, and some vocational learners were back at college for their practical qualifications.
All primary school pupils in Wales, as well as older age groups in Years 11 and 13 who have exams, are expected to return from next week.
