People are seen outside the Old Building of LSE (The London School of Economics and Political Science) in London, Britain, on March 8, 2021. Amid a mixed sense of nervousness and excitement, millions of children returned to schools across England on Monday under phase one of the British government's "roadmap" to recovery from the COVID-19 pandemic. (Xinhua/Han Yan)

People walk past the entrance to King's College in London, Britain, on March 8, 2021. Amid a mixed sense of nervousness and excitement, millions of children returned to schools across England on Monday under phase one of the British government's "roadmap" to recovery from the COVID-19 pandemic. (Xinhua/Han Yan)

A woman sends her children to a primary school in central London, Britain, on March 8, 2021. Amid a mixed sense of nervousness and excitement, millions of children returned to schools across England on Monday under phase one of the British government's "roadmap" to recovery from the COVID-19 pandemic. (Xinhua/Han Yan)

Students are seen on the campus of LSE (The London School of Economics and Political Science) in London, Britain, on March 8, 2021. Amid a mixed sense of nervousness and excitement, millions of children returned to schools across England on Monday under phase one of the British government's "roadmap" to recovery from the COVID-19 pandemic. (Xinhua/Han Yan)

A student walks on the campus of LSE (The London School of Economics and Political Science) in London, Britain, on March 8, 2021. Amid a mixed sense of nervousness and excitement, millions of children returned to schools across England on Monday under phase one of the British government's "roadmap" to recovery from the COVID-19 pandemic. (Xinhua/Han Yan)

A student walks past St Clement's main entrance of LSE (The London School of Economics and Political Science) in London, Britain, on March 8, 2021. Amid a mixed sense of nervousness and excitement, millions of children returned to schools across England on Monday under phase one of the British government's "roadmap" to recovery from the COVID-19 pandemic. (Xinhua/Han Yan)

A woman walks past the entrance to King's College in London, Britain, on March 8, 2021. Amid a mixed sense of nervousness and excitement, millions of children returned to schools across England on Monday under phase one of the British government's "roadmap" to recovery from the COVID-19 pandemic. (Xinhua/Han Yan)

Students are seen on the campus of LSE (The London School of Economics and Political Science) in London, Britain, on March 8, 2021. Amid a mixed sense of nervousness and excitement, millions of children returned to schools across England on Monday under phase one of the British government's "roadmap" to recovery from the COVID-19 pandemic. (Xinhua/Han Yan)

Students queue at an entrance to King's College in London, Britain, on March 8, 2021. Amid a mixed sense of nervousness and excitement, millions of children returned to schools across England on Monday under phase one of the British government's "roadmap" to recovery from the COVID-19 pandemic. (Xinhua/Han Yan)

A woman sends her children to a primary school in central London, Britain, on March 8, 2021. Amid a mixed sense of nervousness and excitement, millions of children returned to schools across England on Monday under phase one of the British government's "roadmap" to recovery from the COVID-19 pandemic. (Xinhua/Han Yan)