European Convention of Human Rights is 1950 actually, its the Human Rights Act the is 1998 and it was enforced in the year 2000. Although we didn't have it enshrined into our law, being a member of the EU makes it compulsory anyway, so it wouldn't have made much difference. Even non-member countries are under some rules and regulations, you can't just go against peoples rights in Europe, ever since the joys of WWII, which I sometimes get the feeling some people would like to actually incorporate into our society...
Common mistake to make
I think its a case of what you do with dogs, provide them with long tiring activities and discipline. There is nothing for teenagers to do, and until there is something to do then they are going to just wander the streets. Obviously providing things to do doesn't solve all the problems, some teens will still rink and take drugs and have sex etc, but it would get many of the younger ones off the street probably.