Don't flip out. They really walk you in to the basics. I myself was placed into Music Theory II - honors and Advanced Sight-Singing III at Ithaca, but from talking to my friends, they truly start you out as if you have no clue. Remember, you're paying them to make you into a musician and to teach you this stuff. Finish up your senior year. If it's anything like mine was, it is truly painful. I took four AP exams that year. Enjoy your summer. Don't practice too hard. You'll be playing (if you're a good student) a minimum of three hours daily, and your new teacher will probably have a lot of bad habits to correct, and it will be much less painful if you take your pieces to your teacher without them already ingrained into the assigned repertoire. As my teacher said to me a million times: "Jason, you're in. You passed the audition. Stop worrying about it."
There will be kids there much better than you at theory, and there will be kids who have absolutely no clue at all, where you wonder what the hell their teacher was doing. Above all, don't freak out. You are there, first and foremost (assuming you are a piano major on pianostreet, go figure) to learn how to play the piano like a professional. Sure, the artists will come back and say they regret not spending more time on sightsinging, but what if they did, and neglected their private instrument studies as a result? I doubt they'd give a damn about sightsinging. Pay attention to your lessons, and any keyboarding classes you might take on sight reading, score reading, etc. That's what you need. Unfortunately, in college, you have to make choices, because your professors will NOT understand. Each has their own demands and believes that you are only taking their class. Do not worry about theory or sightsinging. You'll get what you need, and what you find you don't have when you graduate, you'll know you don't have, and you'll have the resources to learn it.
By the way, you need to know ALL the (chromatic) solfege syllables: going up: Do, Di, Re, Ri, Mi, Fa, Fi, Sol, Si, La, Li, Ti, Do; and going down: Do, Ti, Te, La, Le, Sol, Se, Fa, Mi, Me, Re, Ra (watch out for that one, it's different!), Do. You'll also learn in your career fixed-do and scale degrees, but don't worry about those yet. And, eventually, you'll toss all of that crap out the window to learn how to sight-sing atonal music (not my favorite class

).