As school sports days get underway, students have resumed making large human pyramids, raising concerns about the risk of serious injury.
Teachers have begun posting photos and videos online of students forming structures with as many as 10 tiers.
Despite the dangers, schools have students build the human pyramids for the sake of "the feeling of achieving it all together," according to Ryo Uchida, an associate professor at Nagoya University and an expert on school injuries.