A small change in practice can change everything.
The practice in the children’s swimming team requires a certain distance between every two swimmers. Not only because the distance helps kids focus on the practice but also gives them a proper challenge for those who can to tackle. With enough distance, it takes a lot more energy and skills for swimmers to pass the kids in front of them. When a kid can do so, the other kids are willing to follow wholeheartedly.
The distance is the key. It requires the coach or coaching assistant to monitor it closely, especially for the smaller children.
When the distance is shortened, it creates a problem because passing the kid ahead becomes much easier. Then everyone's focus changes from practice to beating someone. Instead of following the practice and working on their skills, children do whatever needed to "win".
Without realizing the impact of the distance, the practice has turned into something further away from betterment.