I agree with a lot of the comments here and I encourage you to learn more about modern music.
As far as what YOU want to do as a composer is completely up to you. You can simply write only for piano in classical/romantic style all you want and no one will stop you! (obviously)
To me, this modern style and ideas are now more to satisfy oneself rather than the public. What I mean by that is that you should have this really strong desire to compose whatever you want!
If you REALLY want to satisfy the public, then I suggest write Pop, Rock, Hip Hop so Hannah Montana or other pop stars can make it a hit. (I'm not saying that there aren't hit "21st century classical" composers or film scorers, etc with big names)
If you REALLY have this "calling" to write only for piano in romantic/classical style, then how can you let anyone stop you! : ) There will always be a BA program in Composition that will take almost ANYONE as long as you are interested. However, my suggestion to you is to check out ALL TYPES of music from EVERYWHERE, ANYTIME especially in your young age.
I'm 18, a senior in high school, and I'm going to New England Conservatory as a BM Composer this fall. I probably went through similar events that you're going through, looking for colleges, conservatories, comparing, researching, etc... : )