Hi Elaine-
I was in the same exact situation you're in a year ago. Finding good schools and applying to them can be extremely intimidating at first, so here's some advice that hopefully will come in handy during the college application frenzy.
Like airborne91 said earlier, apply to as many schools as humanly possible. If you think you might like to go there, however small that urge is, apply there. Not only does this keep your doors open in case you don't get accepted to the schools you want, but you'll also discover schools that you haven't heard about and which you might like more.
Film schools usually base their decisions on a 50/50 score of academics and creative abilities. So although your portfolio is very important, so are test scores and classroom grades. Remember that schools only use your highest scores in their decisions, so don't be afraid to take the SAT *and* ACT multiple times.
Your portfolio is a collection of your best work, not necessarily your best film work. If the school gives you an option of different mediums for your portfolio, use that to your advantage. Your short story that took months to finish will probably give you a better chance of getting accepted than the Robocop spoof that you made last weekend with your brother and his friends. Some schools will just ask for a resume, but since they are not actually viewing your work, don't hesitate to include *any* recent creative project that you've worked on.
Don't let the school's name get to your head. NYU and USC are just three letter abbreviations. Contrary to the beliefs of some, one does not have to pray to the gods and sacrifice a small goat to be accepted at these schools. Nor does one suddenly gain badass filmmaking skills after being accepted to one of these schools. While they have decent undergrad programs, their fame is a direct result of their graduate film programs, where almost all of their famous alumni come from. I can't vouch for USC's numbers, but NYU's undergrad film program is surprisingly generous, accepting 25% of around 1000 applicants. And one thing I've noticed about a lot of people who get accepted is they think, "Whoa, I got accepted to NYU/USC, I must be hawt!" And then they start running around with this mentality and telling others about how "hawt" they are and soon they forget that there are more schools out there other than NYU/USC and "brand-name" schools. "I don't care how much it costs, Scorsese graduated from NYU, and plus New York is so cosmopolitan!" The truth is that NYU and USC are both 60K+ a year schools, and while USC offers more scholarships than NYU, you have to be the best of the best academically to receive the ones that actually make a difference. Scholarships for NYU are more or less non-existent. Sure, everyone gets something, but a $10,000 scholarship/work-study and $40,000-$50,000 in loans is hardly a "Financial Aid Award." What I'm trying to say is, some people get caught up in the reputation hype, and they don't consider these factors. And because they are the "select few" that got in, they suddenly get cocky and soon they forget why they even came to film school in the first place. I'm not trying to steer you away from these schools, I'm just trying to give you a clearer picture about these schools so that you can make your own decision instead of jumping on the reputation bandwagon. I still highly recommend applying for these schools and if you get in and your financial situation allows it, you will get an excellent film education.
Never be sure that you're not going to like a particular setting until you've visited the place. I had a similar preference for large schools in large cities, but traveling to some other schools really surprised me and made me reconsider what I thought was the ideal setting.
Some other good schools that you might want to consider: UT Austin, Chapman University, Boston University, American University, FSU
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And finally, don't stress about things you have no control over. I know, easier said than done, but once the application's sent, your best bet is just to take it easy and enjoy the last few months of high school with your friends.
And in case you were wondering, I applied to seven schools: Harvard, Yale, Columbia, USC, NYU, Chapman, Syracuse, and WVU (as a safety). The first three were a result of pressure from my parents. The other four schools were the ones I personally wanted to apply to. Guess which schools I *didn't* get into? Okay, just to be clear, I ended up getting rejected by Harvard, Yale and Columbia and got accepted by USC, NYU, Chapman and Syracuse for Film Production ;-) (I got accepted to WVU, but of course no Film major offered there). As you can imagine, it was an extremely difficult decision for me, but I finally made my decision after a month of research and campus visits. I'll be going to Chapman in the fall

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But to give you an idea, I really thought I had little to no chance of getting into USC, NYU, Chapman and Syracuse. And look at how wrong I was. So you probably have a better chance than you think ;-).
For your reference:
My GPA: 4.5 weighted
SAT- 800 Math
730 Reading
660- Writing
ACT- 33
My NYU portfolio-
http://www.adoramapix.com/lotr...portfolio/Portfolio/
My Chapman video essay-
http://www.youtube.com/watch?v=5hrgv7p11hQ
Don't forget the other major factor in addition to academics and your portfolio, your essay. This is your one chance to show the school how and why you are different from the others and also to show how passionate you are about film- something you can't really get across elsewhere in your application. If writing isn't your strong suit, then it will do you a world of good to practice by writing more essays, whether on your own or in English class. Even though I didn't do great on the SAT and ACT writing sections, I credit a large part of the reasons I got accepted to my essays and for USC, the entire film application was writing - a personal essay, a character profile, and a resume. So you can see how important writing is.
Hopefully this has helped at least a little in some way. Good luck and I'm sure you'll do fine!