WE have cruised with Royal Caribbean and Celebrity and our teens had a ball. What is Norwegian like for teens?

It depends upon which ship you are sailing on.

The newest two NCL ships have rock climbing walls and bowling alleys.
The Spirit has a topside disco and large game room perfect for teens. Facilities aboard the ship aren't the only consideration. Activities are also important, such as dance parties and other teens aboard the ship. Plus the Excursions you book while in port.
Each itinerary and ship have different possibilities to entertain your teens.

If you were to post which cruise you are planning to take, and which ship, I'm sure others will reply with more specifics.

On all of the NCL ships I've been on, the teens seem to be having a good time...There are many activities for them if they so choose to get involved....and a lot depends on just how many teens are on board....but there seems to always be something for them to do...if nothing else, there are the video arcades and FOOD....Happy Sailing...

Bob E