One small thing I will say in their defence, is when confronted by an adult following a fight in front of young children, they did (albeit after a few minutes and rather sullenly) move off. Twice now though I have seen them having proper fights (punches to the face etc.), accompanied by the kind of 'fck him up' type commentary, which is just totally inappropriate in a children's playground. As said above, if they were just hanging out there causing no trouble that would be one thing (alhtough I still don't think it's a particularly appropriate place to do so), but violence and agression are not. It doesn't help anyone (least of all the teenagers themselves) to make excuses for their bad behaviour.