What places like the symphony need are simply content that is more relevant to those they want to attract. It's hard to sell traditional symphonic material to younger crowds, so provide that but also a bit of more contemporary stuff.
No, what places like the Symphony need is to get off this stupid idea that kids/teens belong in the opera house. Teens rebel against the older generation, rejecting everything they stand for, and that's a normal and natural phase in their development. Some kids/teens may genuinely be into classical though, and that's fine. Just don't try to push your notion of culture onto the ones who show no interest. Classical music is an acquired taste, not a forcefed one: don't be the Jehova's Witnesses of music.
I used to play the piano as a teenager, yet even then I never really got into the whole classical music thing. But I've matured, learned to appreciate somewhat better audio equipment and the subtleties it exposes in the source material. Classical became a lot more enjoyable since I'm not playing it over shitty cans/buds anymore. I guess being exposed to more classical-ish music in the scores of many great movies, during pivotal and emotionally gripping scenes, has also helped in that regard. I see similar tendencies among some of my friends. So yes, as people mature they tend to broaden their cultural horizons. The opera house will always have an audience; it will always be an older crowd.
An more advanced form of this is the rock band Guster, who is going around to a few select cities and playing many favorite songs that have been re-cast to work with the full symphony playing. The results are spectacular.
That way you get younger listeners to understand why you might want to attend a full symphony, and will probably get them to attend more events. But you have to get them interested first.
That's great, and I definitely applaud artists who try to make classical more accessible by making it more contemporary. But don't expect this to draw the crowds to the opera house anytime soon. There's a huge difference between having a symphonic orchestra accompany you on a contemporary work, and three hours of Mozart.