People don't know things unless they're taught. There's no magic age where you suddenly realize, "Oh, this is how you prioritize your time effectively," or "Ah, okay, if you take the square root of the sum of the square of side A and side B, then you get the hypotenuse of a right triangle!" or "Oh, picking my nose in front of girls doesn't get me a homecoming date." These are things that you learn, things that you are taught either by experience or by someone teaching you.
Age doesn't give you any more or less ability or knowledge, just more of an opportunity to be taken advantage of or squandered. There's the age according to your birth certificate and then there's your life experience and what you've been taught. Those two have nothing to do with each other.