We also have a very well-cruised 14 y/o daughter who has been cruising since she was about 6. Are there kids on cruises who misbehave? You betcha'! BUT, there are also kids at resorts who misbehave, in school who misbehave, in your neighborhood who misbehave... there's just no getting away from them. My daughter is granted the freedom to check herself in and out of the teen programs offered. And she knows the rule... When you check yourself OUT with them you immediately find Mom and check yourself IN with her. And whoa betide the poor child who is NOT where she says she will be when I go to check up on her!!
I have seen my daughter roll her eyes at kids who are out of control. One night at dinner, at the next table, a young boy was talking back fiercely, rudely, and loudly to his parents. My daughter (the only child at our table of ten) was asked what she thought about his behavior by one of our table mates. She laughed and said "I was just thinking... gee, my Mom would rip my head off if I spoke to her like that, and then I was picturing what would happen to me if I dared..." It cracked everyone at our table up!
If you travel with your children from the time they are very young, and if you teach them how to behave in public, towards their elders, and to have manners, you will very seldom find yourself ashamed of their behavior when they are out of your sight!