Secondary school graduates celebrate the end of a school year in Zagreb, capital of Croatia, on May 22, 2018. The celebration "Norijada" (Crazy Day) is held annually nationwide to mark the end of a school year. (Xinhua/Marko Lukunic)

Secondary school graduates celebrate the end of a school year in Zagreb, capital of Croatia, on May 22, 2018. The celebration "Norijada" (Crazy Day) is held annually nationwide to mark the end of a school year. (Xinhua/Luka Stanzl)

Secondary school students celebrate the end of a school year in Zadar, Croatia, on May 22, 2018. The celebration "Norijada" (Crazy Day) is held annually nationwide to mark the end of a school year. (Xinhua/Dino Stanin)

Secondary school students celebrate the end of a school year in Zadar, Croatia, on May 22, 2018. The celebration "Norijada" (Crazy Day) is held annually nationwide to mark the end of a school year. (Xinhua/Dino Stanin)

Secondary school graduates celebrate the end of a school year by performing traditional quadrille in Osijek, Croatia, on May 22, 2018. The celebration "Norijada" (Crazy Day) is held annually nationwide to mark the end of a school year. (Xinhua/Dubravka Petric)