I graduated high school in 3 years, mostly because it was easy and boring for me… I didn’t decide this until my junior year, but since I had (luckily) taken such full schedules my first two years anyway all I had to do was take some after school online classes for a semester to get the senior year requirements my school had out of the way (government/economics classes, etc.) And then I went to college, I was 17 when I moved out and everything so it was a little weird… that’s probably the biggest drawback! So a warning to all of you who are trying this, if you go off to school somewhere and try to stay out and party like everyone else, you’re still going to have a curfew and that SUCKS! But a few months into the school year I turned 18 and was able to stay out late, get a checking account, etc.
Just make sure you don’t slip, because once you do it’s almost impossible to graduate early. I had two friends who wanted to do this with me and both of them slacked off a little bit and ended up starting their 4th year.