I find it interesting that this phenomena in teens is only true in the USA. Other countries kids use full sentances, they borrow the dress and fashion, but retain thier curiosity. In the USA, There is a decided passage where they disengage from adults, take a position to provide resistance to any request. While the drama of growing up is the same world wide--- only the USA breeds disinterest, mono-sylable, fail to use mind aspects of our youth culture...
We are the only nation that has kids slumping in seats, unwilling to cooperate. While elsewhere they are eager to learn - what happens in USA that isn't elsewhere?