We've had teenage gangs in Manchester for 200 years, it's nothing new. I've got a book on it actually, the Guardian's outrage that poor young kids resort to violence, was quite something
The circumstances which lead to youth violence are generally the same the world over, poverty, poor housing and a lack of education and opportunity. But to solve that requires major political will and money - much easier(yet less effective) to stop and search people and be *seen* to do something than *actually* do it
I suppose the Great Divide in society is between those who believe that all evil (and all positive things too, like being successful) are down to individuals. And those who think it's more complex. But once you start arguing for complexity, it becomes well - complex, and therefore hard to analyse. Let alone to solve.