Students have their health codes checked before entering a high school in Beijing, April 27, 2020. Senior students in Beijing’s high schools resume their studies on Monday after schools were shut for months because of the coronavirus.(Photo: China News Service/Hou Yu)

A worker carries out disinfection for luggage of a students at entrance of a high school in Beijing, April 27, 2020. (Photo: China News Service/ Hou Yu)

A student has her temperature taken at entrance of a high school in Beijing, April 27, 2020. (Photo: China News Service/ Hou Yu)

A student has her health code checked at entrance of a high school in Beijing, April 27, 2020. (Photo: China News Service/ Hou Yu)

A student has her temperature taken at entrance of a high school in Beijing, April 27, 2020. (Photo: China News Service/ Hou Yu)