Students attend a class at a high school in Hangzhou, east China's Zhejiang Province, April 13, 2020. Students in their final year of senior and junior high schools in Zhejiang returned to school for their new semester on Monday. (Xinhua/Huang Zongzhi)

People walk past an infrared temperature detector to enter a high school in Hangzhou, east China's Zhejiang Province, April 13, 2020. Students in their final year of senior and junior high schools in Zhejiang returned to school for their new semester on Monday. (Xinhua/Huang Zongzhi)

Students attend a class at a high school in Hangzhou, east China's Zhejiang Province, April 13, 2020. Students in their final year of senior and junior high schools in Zhejiang returned to school for their new semester on Monday. (Xinhua/Huang Zongzhi)

Students attend a class at a high school in Hangzhou, east China's Zhejiang Province, April 13, 2020. Students in their final year of senior and junior high schools in Zhejiang returned to school for their new semester on Monday. (Xinhua/Huang Zongzhi)