A student wearing a face mask studies in a classroom at a middle school in Yinchuan, northwest China's Ningxia Hui Autonomous Region, March 25, 2020. Students in the final year of middle schools and high schools in Yinchuan resumed classes on Wednesday. (Xinhua/Yang Zhisen)

Students have a video class at a middle school in Yinchuan, northwest China's Ningxia Hui Autonomous Region, March 25, 2020. Students in the final year of middle schools and high schools in Yinchuan resumed classes on Wednesday. (Xinhua/Yang Zhisen)

Students have lunch at Yinchuan No.9 High School in Yinchuan, northwest China's Ningxia Hui Autonomous Region, March 25, 2020. Students in the final year of middle schools and high schools in Yinchuan resumed classes on Wednesday. (Xinhua/Yang Zhisen)

A student picks up her meal at the canteen of Yinchuan No.9 High School in Yinchuan, northwest China's Ningxia Hui Autonomous Region, March 25, 2020. Students in the final year of middle schools and high schools in Yinchuan resumed classes on Wednesday. (Xinhua/Jia Haocheng)

Students take an exam at Yinchuan No.9 High School in Yinchuan, northwest China's Ningxia Hui Autonomous Region, March 25, 2020. Students in the final year of middle schools and high schools in Yinchuan resumed classes on Wednesday. (Xinhua/Yang Zhisen)