I just came back from Rhapsody of the Seas and I heard that 12-14 years old have their curfew at 12:00. What it means is that you have to "disapper" from any public areas. Sometimes the teens supervisor might have some activities after midnight and that is usually in the kids/teens facility area. 15-17 years old's curfew is at 2:00am.
I have heard that RCCL is starting to have a cufew for anyone 17 and under. I believe it was 1 am. I know they were testing the program on the Voyager when I went this past May, they would have deck patrols every 20-30min and saw them send a lot of people to their cabin. If they have a policy, it'll be printed in the compass you get every night in your cabin. Also from what I understand, this policy was going to be only for peak travel seasons like holidays, spring breaks, and the summer. I know it sucks.
I was on Explorer on 8/23/03 and there was a midnight curfew, where we had to be in our cabins/with parents/in Optix after midnight. But no one paid attention to it, my friends and I were out way past midnight, right next to a security guard and he didn't care. No worries man