My family are very involved with childrens rugby. We can predict which children will engage in unsportsmanlike behaviour by talking to the childrens parents. Those children who are rewarded by their parents for each try they score individually are most likely to be culprits. In a team game, reward of individual achievement instead of team achievement in less talented players
yields players with the worst conduct less likely to pass to team members and also most likely to continue bad attitude to successful team members off the pitch.