Typos notwithstanding, there's no physiological evidence that I'm aware of that maturation must happen after 18. In fact there is much evidence that in many times and places it happened, and still happens, much earlier. So the problem isn't that college freshman are too young, but that they are too immature.
As the parent of a child accelerated significantly in school, this is a pressing issue for us. My child must be more mature than her peers if she's going to be accepted into classes with older students. Ditto if she expects to start college early. Obviously there's such a thing as too mature too fast, but at the same time there's no developmental reason not to teach those skills earlier and more rigorously. Many cultures have done so and still do.
