Good question …

… Montessori schools are exceptionally successful. So why aren’t there more of them? | America Magazine.

Once a child is ready to walk, she will expend tremendous effort to do so, but only when it is the right time in her development. So it is with other skills. Trying to teach, say, writing, on a rigid schedule will only convince a child that she is unable to do so, sapping not only that endeavor but her self-confidence and willingness to learn more generally. We can all attest from our personal experience that we easily become frustrated and despondent whenever we have to do things that are either far too easy or far too hard; but when our work is right at the edge of our comfort zone, challenging but doable, not only are we better at tasks, but we often find them positively thrilling.