China has designated June 1 day as the International Children's Day since 1949. On this day, the school generally organizes related group activities for this purpose and requires students to dress formally.
Source background
In order to mourn the Lidice tragedy and all the children who died in the war all over the world, oppose the abuse and poisoning of children, and protect children's rights, 10, 1949, 165438, the Council of the International Democratic Women's Federation was held in Moscow, and representatives of China and other countries angrily exposed the crimes of killing and poisoning children by imperialists and reactionaries from various countries.
The meeting decided to take June 1 day every year as International Children's Day. It is a festival set up to protect children's rights of survival, health, education and guardianship, improve children's lives and oppose child abuse and poisoning. At present, many countries in the world have designated June 1 as Children's Day.