Try ocean village i ve done it twice in carrabean lots of age groups and good mix of people very friendly not stuck up.
Believe me Ocean Village is fab for kids of all ages, and good on the budget too. My son enjoyed the teenage clubrooms, discos,and big brother etc. contests that they get the kidsinvolved in as well as all the sport. Or the Royal caribbean ships are fantastic but a little more price.
Most cruise lines have teen clubs. Royal Caribbean would be perfect - they cruise from Southampton, and have loads to do for teenagers, from rock climbing, surfing, karaoke, discos - and the main street in the centre of the larger ships doesnt just have formal dining restaurants but pizza and burger bars, ice-cream parlours, amusements and much more. The swimming pools have kids areas with water cannons, the 'H2O Zone', 18 hole putting green etc.. I would seriously look at Royal Caribbean - the ships have better facillities and more choice (both in what to do when onboard, and actual ship itineraries.
Don't rule out Carnival - slightly cheaper than Royal Caribbean, and said to have larger cabins than the other lines (we're giving them a go in December) We often have 3 adults in one cabin and have never found it too crowded on Royal Caribbean or Princess. One in a cabin is SOOOO expensiv.