I think it's unfortunate that schools aren't teaching financial responsibility while children are subjected to intense marketing campaigns and peer pressure to keep pace with trends and friends. I think schools can only go so far as a child's financial reality and perceptions are influenced by their immediate and extended family and local community. By nature, we tend to be very generous with our children which can set the expectation bar pretty high. I think there are two key lessons to learn: 1) budget management / tracking and 2) budget estimation -- forcasting spending versus income. There's also a longer term message around future planning; ie not spending 100% of income.
I'm not sure how much children can learn outside of actual experience so I've tried to come up with focused experiences that convey aspects of financial responsibility. My teenage daughter is on a twice yearly clothing / entertainment budget that we negotiate and she has responsibility for managing. When she's out of budget there are no new cloths or itunes until the next budget cycle. We discuss how many hours she's have to work at one of the job's her older friends have to earn that money.
I also try to help her manage impulse buying when she's shopping by playing "gong show". We make a list of the things she "needs" and agree on it. She can still shop for other things but could get "gonged" and lose everything. This forces her to prioritize whim items and consider whether the next one is worth losing everything -- she's not sure whether I'm tracking number or cost of items so the cheapest most important thing is best bet.