<p>I applied to college as a junior in high school, had a successful run at it, and matriculated at (obviously) MIT that Fall without a HS diploma or GED. Here are my two cents:</p>
<ul>
<li><p>Do your research and see what each particular school’s attitude and/or philosophy is toward admitting young students, specifically if you do not plan to graduate from HS.</p></li>
<li><p><em>State schools</em> care a lot more about whether you will have met particular curriculum requirements upon matriculation than do private schools. For example, I would not have been considered at U Michigan (I called them to ask) because I was missing half a credit of economics, or some such nonsense. I don’t recall the <em>particular</em> coursework they wanted, but that was the gist. I was accepted at Georgia Tech under the condition that I earn a summer school credit in a foreign language. None of the private universities cared about the particulars of my curriculum. They were more interested in its overall quality and depth. I took a <em>lot</em> of courses in high school, but was still missing a couple of things since I focussed far more on advancing in my school’s core areas of curriculum than on (what I considered at the time) peripheral requirements.</p></li>
<li><p>Don’t apply as a junior because you think it’s impressive; do it because you truly believe, and can justify, that it is the best thing you can do for your intellectual and social development. If you don’t have a good enough reason for attempting this potentially risky maneuver, you risk (a) not being taken seriously by admissions departments or (b) stunting your growth in one way or another by prematurely entering a college environment. Sure, there are 16 year old grad students out there…and, unless they are SO brilliant as to overcome it, their social skills are often a risk to the realization of their potential once they hit the <em>real world</em>. It was hard for me to find my discipline at MIT. I eventually did, but I made a few follies of youth along the way. All college students must find that balance, but I dare argue it is more difficult when you’re essentially a kid when you first walk in the door.</p></li>
<li><p>Your senior year of high school is awesome (as I understand it). Surely, so is your freshman year of college. Why not have both? The reason I left my high school was because it was a sub-par public school in a state with terrible education. I had already taken nearly all of my school’s APs and also accumulated a fair number of credits at the local university. The next year, my school’s plan was to keep me technically enrolled but to send me to the local university for almost all of my courses. That was an unacceptable scenario. If they were going to send me to college, I was just going to <em>actually go to college.</em> I was well prepared for MIT by sweat and blood alone if nothing else, but getting in so young didn’t mean that I was head-and-shoulders above my classmates there. Many of them simply went to better high schools than I did: schools that could accommodate their needs. If my high school were like some of the schools I learned about through my MIT classmates, I probably would have stayed through 4 years as they did.</p></li>
<li><p>All the above said…I’m glad I went to MIT when I did. It was exactly what I needed, even if it took a bit of getting used to. I wouldn’t change it.</p></li>
</ul>
<p>P.S. After grad school, I got a teaching certificate and went back to try to right some of the wrongs of my own education, and to repay the mentors who helped see me through. I eventually found a student like myself…a sophomore with a ton of energy and a sharp mind, but insufficient opportunities for growth. He and I worked on ever more advanced math and physics every day for two years, and became very close. He got into his dream school and was able to skip 3 semesters of math. Feeling that my debt was repaid, I respectfully bowed from teaching to pursue other opportunities (and so that I could repay my <em>real</em> debt 
). Anyway, the above story is mostly to show how deeply my high school experience affected me…and to show, at least through indication, how seriously I needed to go to college when I did. I think another year of high school would have hurt more than helped.</p>