As a society, we define ourselves by time way too much. We track accomplishments and declare them ordinary, menial things if accomplished on schedule, and allow ourselves the pleasure of being extraordinary only if we manage to accomplish the same things as everyone, but ahead of schedule.
By assuming children will walk, talk, piss, whatever, at a certain age, we not only box them in and limit their growth, we foster a sense of urgency, the idea that the faster we do everything, the better.
By assuming teenagers will be a certain way throughout their teenage years, and that they can only handle so much (they aren’t adults, remember?), simply, what did we do to the infants again? Oh yes, box them in a limit their growth.
We need to look at everyone as seperate individuals, and allow them to progress as they will, step back and give them the space they need to move forward at their own pace. If they move ahead painfully slow, let them, encourage them, be there to help if they ask. If they move ahead ridiculously quickly, let them, encourage them, be there to help if they ask.
Unfortunately, I recognize that there is currently no good or efficient way to do any of this, and that the current system works for the majority of people (I think, who knows how many other screwy people are out there that we have no idea about). Until we make leaps and bounds of progress as a society the system we have now is probably going to remain in place.