It's not the teenagers it's the parents raising them who are the problem. They are the ones not teaching them respect, to think things through etc etc kids learn respect, manners, responsibility from their parents, family, community so if they are badly taught well...
It's not just parents, it's society as a whole that is the problem. As the old saying goes "it takes a village to raise a child" these days the onus on raising the next generation falls on parents and teachers - the remainder of society takes no accountability whatsoever.
I'm not a parent myself, but I don't think it is practical for a parent (or teacher) to be everywhere at anytime to keep an eye on what their kids are doing. Also a certain amount of time away from authority also helps develop independence and ability to think things through, I find a lot of the younger generation now are Shit scared to make any decisions as they are so used to taking directions. How they are meant to adjust as an adult and make decisions with that kind of upbringing confuses the hell out of me.