Elberry at The Lumber Room has an excellent solution to feral youths and knife crime:
I imagine there are several thousand, or hundreds of thousands, of young men carrying knives ‘in self-defence’ who will, however, pull it as soon as they imagine a confrontation is in the air. They would be far better to carry expandable batons, and far less likely to accidentally kill someone. They would do even better to stay at home reading Sir Philip Sidney.
Personally, I would recommend The Anatomy Of Melancholy, but just staying indoors, reading improving literature, seems to me a splendid idea.