Schools in England reopened for all pupils on Monday for the first time since January.
Millions of students resumed in-person lessons after spending weeks learning from home or remotely over live streams.
While schools had remained open for parents who work in frontline roles - such as health care workers - once England saw a consistent decline in cases, Prime Minister Boris Johnson announced on February 22 that schools would be able to reopen from March 8.
Pupils aged 11 to 16 are being asked to take three Covid-19 tests on site and at home over the initial two weeks when returning to school, and then test themselves at home twice weekly.
Britain's Department for Education is also advising secondary school students to wear face coverings when social distancing cannot be maintained, including in the classroom.
But primary school children - aged 5 to 10 - are not being asked to carry out Covid-19 tests or wear face masks on their return.
Northern Ireland
Some children are also returning to classrooms in Northern Ireland for the first time since December, after enforced remote learning ended on March 5.
In a briefing with journalists, Johnson said Monday marked a “big day and an emotional day” for families in England.
“We all know that the education of our children is so important that the greater risk now is keeping them out of school for a day longer," he said.
“I want to thank all the teachers who have got their schools ready and who have been teaching throughout the period – whether that is remotely or in person. Your work has been astonishing.”
