Photo taken on April 21, 2020 shows a warehouse storing epidemic prevention and control materials at a middle school in east China's Shanghai. In Shanghai, classes for senior students in middle and high schools will resume on April 27. Those schools have been actively making full preparations for the reopening to ensure the safety of the students and teachers. (Xinhua/Liu Ying)

A teacher makes preparation at a temporary isolation room at a middle school in east China's Shanghai, April 21, 2020. In Shanghai, classes for senior students in middle and high schools will resume on April 27. Those schools have been actively making full preparations for the reopening to ensure the safety of the students and teachers. (Xinhua/Liu Ying)

Photo taken on April 21, 2020 shows thermometers prepared for all classes at a middle school in east China's Shanghai. In Shanghai, classes for senior students in middle and high schools will resume on April 27. Those schools have been actively making full preparations for the reopening to ensure the safety of the students and teachers. (Xinhua/Liu Ying)

A disinfection robot works at a classroom in a middle school in east China's Shanghai, April 21, 2020. In Shanghai, classes for senior students in middle and high schools will resume on April 27. Those schools have been actively making full preparations for the reopening to ensure the safety of the students and teachers. (Xinhua/Liu Ying)

Photo taken on April 21, 2020 shows the temperature detector at the entrance of a middle school in east China's Shanghai. In Shanghai, classes for senior students in middle and high schools will resume on April 27. Those schools have been actively making full preparations for the reopening to ensure the safety of the students and teachers. (Xinhua/Liu Ying)

Photo taken on April 21, 2020 shows a warehouse storing epidemic prevention and control materials at a middle school in east China's Shanghai. In Shanghai, classes for senior students in middle and high schools will resume on April 27. Those schools have been actively making full preparations for the reopening to ensure the safety of the students and teachers. (Xinhua/Liu Ying)