KB, seems to me you're sad because you're impotent to make a noticeable difference, trying to push back the tide. The main problem is you only have your own frame of reference to work with. I'm quite sure we seemed as revoltingly materialistic and shallow to our parents as the kids in your class do to you, and so on back for many generations.
The difference between you and your parents is that the population is expanding, and therefore sum of knowledge, technology and change are also expanding, packing greater change into less time.
It's easy to think that the further back you go, the more civilised things were, but go back more than the blink of an eye and things were pretty savage. Existence itself would've taken up plenty of your thinking time, unless you were one of a tiny portion of life born into wealth. Dwelling on where you're getting your next meal from probably outweighed pondering whether to buy a cashmere poncho or not.
Existence is now taken for granted by the vast majority, especially the young. Even people well into their 40s and 50s can now rely on the state to guard them from all evils (so they'd have us believe), giving everyone much more time to concentrate on that material item they've had their eye on.
A secondary problem is that kids are no longer driven to thinking in terms of pure theology/science/philosophy, but in applied versions of each. This is undoubtably a good thing for many (and another debate entirely), but again it removes focus from the big knobbly existential questions that give you the set of values you live by, making it easier to follow the pack, buy into the marketing.
This may seem a bit far fetched for nippers, but I'm sure what you're seeing is a lesser version of the above mirrored, from the parents and peers, in the eyes of the kids your dealing with.
For what it's worth, I like to think of it as cyclical. It's just that the cycles are rather long, measured in generations rather than years. It's also a little comforting to know that england seems to be at the forefront of this ignorance-is-bliss revolution (excl. US), so if you can't take anymore then feel free to wander over to france, down to argentina, or across to japan, where you'll find slightly more thought, slighty less cash.
Alternatively, hang around here and surround yourself with people for whom life is still of some interest. And don't worry too much, disinterested kids do occaisionally become interested adults. You can spot them easily by their universal love of v-twins....
Cheers,
Ali