I applied for early admission to UNM. I applied fairly late (I don't remember if there was an explicit deadline, but if so I was before it) and hadn't heard back by the first day of my senior year of high school. I called the admissions office at lunch from the high school, and they said, "Sorry to have not gotten back to you in time. You've got good letters of recommendation and you already have six credit hours at UNM with a 4.0 GPA. We're going to admit you."

I told people at the high school goodbye, left before the end of the day, and never went back to that fucking place.

That's how I did it. Your mileage may vary.

You could probably drop out, get a GED, go to community college for 2 years, and then transfer to the school that'll give you a 4 year degree.

With that said, I think some states have different rules in terms of what age you're allowed to drop out at. For example, Illinois requires students to be 17 years of age (and receive parental consent, of course) to drop out. At that point you're better off just finishing high school. even if you want to rapidly track into college.

It's really not that difficult. For formality's sake you could pick up a GED, but I think most colleges don't have a HS diploma as a strict requirement and would waive it if they did (assuming some evidence you're ready).

EDIT: I speak for the USA only.

Aside from what others have suggested, I went to a college called Simon's Rock which accepts mostly high school sophomores. I don't have a single close friend who didn't get into college without a high school diploma.

And before you ask, our admissions are close to 100%, and our academics are some of the best in the country.

Lots of colleges have early admission. I met all the qualifications to go to college after my junior year of high school, without a HS diploma, but I didn't find that out until my Senior year.

Was pretty pissed off at my guidance counselor for not telling me!