The average child spends eight-to-ten hours in school every day of the week -- getting up before dawn, standing in the cold, getting on a bus, and sitting through learning materials that have been pre-determined to be necessary for their success as students. The average American elementary schooler spends 934 hours in school per year, and many spend much more time at boarding schools, after school programs, and after-school detention and suspension.
To what end?
Why do we spend so much time, money, and resources on schooling? And why do we make it compulsory for children to attend a pre-approved schooling system?
"Well that's obvious, it's so they can be educated."
But educated in what? If we allow the assumption that schooling = education (which we ought not to, but will for sake of argument here), then the content of what the schools teach is going to determine in what the children are educated. If schools teach math, then children will become educated in math, for example.
"Educated in the skills and knowledge they need to know to be successful."
This yet again raises another question: successful at what? Life is complex and people set different ends for themselves. Sometimes (oftentimes?) they just accept the ends that they find themselves wanting without much critical reflection. There's no common definition for what it means for children to be "successful."
"Obviously what we mean is that we want them to have the skills and knowledge necessary to become successful adults."
Giving young people the cognitive and educational resources they need to "become successful adults" is a noble end, of course. It is an incredibly haughty and presumptuous goal, though. What does it mean to "become successful adults?"
There are libraries full of books by philosophers reflecting on what the purpose of life is, and what it means to be fulfilled and successful for adults. If childhood is defined by schooling, and if schooling is defined by the ability to become a fulfilled/successful adult, then childhood is defined by the ability to become a fulfilled adult. The problem is, nobody knows what this means, and even if they did, it is different for everybody.
The absurdist philosopher Albert Camus wrote in The Myth of Sisyphus that there is no objective meaning to life. Life is, in Camus' words, absurd. We have to come to grips with this fact and create our own meaning from this lack of meaning. Only when we can delight in this fact can we find our own drive and fulfillment. To assume that this is the same for all the students in a classroom, let alone all the subjects of the federal Department of Education, assumes that there is a standard by which one can create meaning from the absurd.
In short, if the point of childhood is to become a successful adult, then we should be even more opposed to standardized schools. The ability to craft meaning and fulfillment from the world is something that is unique for each individual person and can only be crafted through experience with and interaction in the world. The point to childhood is no different than the point to adulthood: there is no point. The point is to find meaning and fulfillment for ourselves. This is a deeply personal and subjective experience, and one that cannot be taught via scantron bubbles and school-wide textbooks.