It's about the ignorance to the reality of adolescence
This is a discussion about youth and that the young could ever develop to be violent. We are to watch this video as ignorantly wise; steeped in our comfort of peacefulness, irritated by minor ails, distant and dull, tall from the possibility of conflict, stupidly expecting our children would magically become mild.
Throughout the prevailing peacefulness of the movie, we experience sudden punctures of unbelievable force. We're caught off guard. This is a critique of our hollow enlightenment: false peace to reasonless butcher. The viewer is entitled to consider that, the capacity to be absurdly cruel, is not a monopoly to the older.
Furthermore, there is the scene of the lottery. This expertly discusses the experience of younghood to a cold-hearted, rigid environment, an aged world. For once, the young have the secrets in one hand, and the most incredible violence in the other. The meaningless promises to them have evaporated. There's no revolution: only destruction.