I recently flew to and from the west coast, and during that time the only rude behavior I encountered was perpetrated by adults. In fact, the most pleases, thank you’s, and excuse me’s came from young boys and girls.
A telling example: on the flight home I was seated next to two brothers, both roughly middle school age. Not seeing parents seated anywhere near them, I was a bit concerned about the next two hours. Instead of being loud, rough, etc. (how I often assume unsupervised children will act), these boys were quiet as church mice. In fact, the younger of the two got exceptionally sick during the rough takeoff from Reno, and even in his compromised state he always said excuse me and thank you.
What these boys reminded me of is that as parents we largely determine the future of social behaviors and how society will look. We are taught to say please/thank you/excuse me; we learn how to treat each other. If these brothers are any indication, vital social behaviors are still being engrained in our young, and the hand baskets to hell we are supposedly already in are actually collecting dust in banal conversations.