A student prepares to enter the campus in Sydney, Australia, May 25, 2020. Some primary and middle schools in New South Wales resumed classes on Monday. (Xinhua/Bai Xuefei)

Students pass by an electronic placard welcoming their returning at a primary school in Sydney, Australia, May 25, 2020. Some primary and middle schools in New South Wales resumed classes on Monday. (Xinhua/Bai Xuefei)

Students enter the campus in Sydney, Australia, May 25, 2020. Some primary and middle schools in New South Wales resumed classes on Monday. (Xinhua/Bai Xuefei)

Photo taken on May 25, 2020 shows an electronic placard reminding people to remember social distancing at a campus in Sydney, Australia. Some primary and middle schools in New South Wales resumed classes on Monday. (Xinhua/Bai Xuefei)

Students prepare to enter the campus in Sydney, Australia, May 25, 2020. Some primary and middle schools in New South Wales resumed classes on Monday. (Xinhua/Bai Xuefei)