Each class of 45-50 forms one row. Initial training is by class teachers, themselves coached by trainers from the Collective Athletics department at Pyongyang Athletics College. Practice lasts four months, or six for a major event. As the date draws near, training may start at 7 am and last till midnight. That's not the only burden.
Much training is in winter, and gulping hot soup causes lips to crack.
Beating is the routine penalty for any infraction - such as peering to see what the child behind is doing. And woe betide anyone who plays a wrong card - above all if this shows up as a blemish on the Dear Leader's beaming face. Absolute perfection is demanded. Parents too are burdened. They have to provide the soup, and recently the cards as well - which used to be free.