Don't expect very many under 21 passengers on this 14 day cruise, especially during school in session season. We did this cruise in January, and I don't think there was 20 passengers under 18 on board. However, the 3 or 4 teenagers onboard didn't have any problem getting time on the video games in the teeny-weeny arcade.
I have to agree with the above noter. I took my 19-year-old daughter on this same cruise last year and we had about 20 or so who were under 21. She still managed to hang out with the younger crowd most days. Somehow the "kids" all managed to find each other. We were in Barbados when I guess the last of them met her because one guys said, "Oh, so you're the 19 year old." She must have been the only one.
Still had a wonderful time, though.
BTW, head on over the www.cruisecritic.com, click on "Boards" and go to "Celebrity Roll Call" on the message board and sign up. We have a thread over there with others who are going. Not sure if any of them have younger people this time, since I'm going alone this year.