<p>Cornell has something called Urban Semester, where for a semester, you do internships and/or classes near Cornell Medical School near the Upper East Side of Manhattan.</p>
<p>it looks like the program is open to all students from any school in the region. basically, you're going to have to tell your college that you're taking a semester off, so that way, you can enroll at the NYU program. i'd just make sure the credits you earn are transferable so you don't "waste" a semester's worth of time.</p>
<p>A lot of ivies and high caliber schools do have programs for high school students to do things in the summer. Sometimes this can include college courses while other times it might be a special program.</p>
<p>You can apply to be a "visiting student" for a semester or year at Harvard. It's not a big program, but it is an interesting alternative to going abroad for students at small LACs.</p>
<p>There are a group of LACs in the Twelve College Exchange where you can go to another one for junior year or a semester.....(Williams, Amherst, Wellesley, Bowdoin, Middlebury, Wheaton, etc.) Come to think of it, there is an Ivy in the program......Dartmouth. (unless my info is dated)</p>