<p>A lot of elite schools actually do give students the opportunity to apply for advanced standing that may allow them to graduate up to a year early. Whether or not a particular AP or IB exam can be used to substitute for various courses is judged on a case by case basis; a school might let a student skip intro calc with a 5 on BC, but not give credit for AB, or might allow a 4 or 5 on Spanish to fulfill a language requirement but determine math placement based on a test regardless of prior exam scores or coursework. </p>
<p>Very few students take advantage of advanced standing because, apart from the desire to spend four year on campus, there are plenty of practical reasons that graduating earlier is a bad idea in most cases. In most majors - including STEM - getting a degree isn’t just a matter of completing a sequence; even once you get into advanced level courses, there are plenty of courses to take. An extra year gives you more time to build an impressive transcript that suggests exposure to a range of topics in your field, something that will be useful whether graduate school or certain professions are your next step. In other cases, graduating in three years might lead to a tougher course load each semester, since you have less time in which to space out your most difficult required courses. </p>
<p>To the extent that top schools do treat transfer students and incoming freshman differently, they may have pretty good reasons for doing so. I’d wager that Yale is taking very, very few transfers from CCs or regional four year colleges. On the other hand, the majority of incoming freshman who have some college credits have probably been commuting to local schools where an “A” in an intro course might not say much about a student’s readiness for the next in the comparable sequence in an elite school. There’s also a practical component - in the rare case that a potential CC transfer is spectacular enough to catch Yale’s eye, it simply isn’t reasonable to expect a student to write off two years of full time education as a loss. If you want a chance at that student, you simply can’t make him or her start over. It is a lot easier to tell a freshman that the summer enrichment course he took as a high school student doesn’t count.</p>