South Korean dropout here. Yes you can. You take a test granting something legally equivalent to high school diploma (as I understand, GED in US is something similar?) and there is a legally mandated conversion table from test score to transcript which is accepted by all universities.
So a 14 year-old (western age) can just take a test, graduate from high school in a year, go ronin for another and matriculate by 16? That sounds incredibly interesting. I'd love to hear your story, even if its a short summary.
Yes, in the United States, you can take a GED to graduate but that's usually reserved for adult high school students. I've never heard of it being used to skip high school and go straight to college admissions.
The closest parallel that I know of is Early Bird/Junior Admission. Essentially, one must first obtain all the credits required to graduate, and then as a high school junior apply to a college/university (although that only seems to be an available option for a few colleges) but it isn't exactly the same as what you're describing.
There was a stoner kid in my US magnet school who, to the best of my understanding, did the GED to graduate at 15, then went on to the local community college. As far as I know they've always taken high schoolers for credit courses so this route would ultimately result(if aiming for a four-year bachelor's) in transferring with a pile of course credits at 18.
