The young, like other ages of troublemakers, do what they do because they know full well they`ll get away with it
The government (no matter which it is as we live in a one-party state) deliberately do nothing because they want as big a possible excuse to remove more basic freedoms and bring in a more centralised and 1984-style police state.
Rather than bring back the birch (twice as much violence, same outcome), how about bringing back the stocks and encouraging loads of people to throw rancid fruit veg and other crap at them while others laugh at them and take pictures and films of the event to be shown all over the place? I`m sure the ABSOLUTE humiliation of them being reduced to tears in public would really make them think twice about doing such things again.