if you did that, obese kids would be the norm, school (if kids went at all) would end up teaching the finer points of getting to the next level of supermario. Kids need guidance, but also a forum for innovation.
i think you missed the subtlety of travisjeffery's post. the montessori method of teaching is all about "Let your kids do what they want to do.". most young children have a natural "i'm full" signal that prevents obesity (any parent knows this). most kids are naturally curious. many of our greatest historical thinkers did not attend school and had lots of "do what you want" time. the "let kids do what they want" works surprisingly well when they have opportunities to explore and good role models.
my only other addition to the travisjefferies post is "and allow children to fail". too often we don't allow children to learn from their failures. this is part of being a "self starter". you don't fear failure because it has happened so many times though personal experimentation that you have an intrinsic understanding that "it's no big deal, i'll eventually figure it out".
