<p>Having worked in the Admissions office as a college student, I know that after Early Decision letters have gone out and people have signed their forms and turned in commit letters, schools will share their lists of admitted students with other peer institutions. This was done so that they could catch those that applied to more than one school ED, which they weren’t supposed to.</p>
<p>Other than that, I don’t seehow a college/university would know what other schools you applied to. Though I have heard of rumors that the Ivies share applicant lists with one another and sometimes negotiate amongst themselves to see which one(s) will admit the top students who applied to all of them. However, this rumor can be neither confirmed or denied, so take it for what it’s worth.</p>