You could argue that if someone is starting college 3 years early, they may have 3 more years of lifetime earnings over which to amortize the cost of a college education, so they should be willing to borrow more than a normal-age college student. The counter-argument is that a gifted 15yo is still a minor and should not be taking on debt. I'm not sure which argument is stronger.

"To see what is in front of one's nose needs a constant struggle." - George Orwell