<p>To get in as a junior, you have to make a convincing case that you have exhausted your local academic resources. Besides this, you probably have to be a higher quality candidate to get in as a junior. I wouldn’t bother applying as a junior if there are major science AP’s (e.g., physics, chem, bio) that you won’t have finished by the end of the year or if you haven’t finished your school’s math sequence, for instance.</p>
<p>It won’t hurt your senior year chances to have gotten rejected junior year.</p>