Answer:
I'm not sure what subject this is, but I'll try my best.
There's a series of possibilties on how one can go to college under 18 for over 3 months.
- It depends on the country traditions.
A: In places like South Korea or other Asian countries particularily, a child would be a year older. For example, if you were born in 2000, you'd be 22 y/o in the US but 23 years old in SK.
- IQ?
A: Intelligence and speed plays a huge role in this matter. It's simple, the faster and smarter you are, the more faster you go up the levels. Of course, the course(s) you take or where you study also plays a huge role. For eg; Most public schools in the US/UK will most likely not let you jump up and down the grades beyond age. Only in very special circumstances will that pan out.