I think that would really depend on your school. I've heard of schools where they would likely kick you out. The school I go to has an entire floor of one dorm dedicated to LGBT students. I think also a lot of schools would simply move you to a dorm that matches your identity, regardless of where you are at in transitioning. I would check to see if your school is listed at www.campuspride.org. They list LGBT housing policies at that website.