How will my child learn anything if no one teaches them and no one tells them what to learn?
Ah, the classic question. Let’s start with the learn anything part.
Children learn. It’s what they do.
Our ancestors evolved to live successfully in a difficult environment (dry savannah) by observing our environment, learning from each other, sharing, experimenting, creating, and exchanging knowledge. What our ancestors almost certainly did not do was teach their children in an explicit, systematic, and structured way. They may have told children the name for particular plants or how to tell the difference between two similar looking plants, but this wouldn't have involved a systematic curriculum. (In many cultures, asking questions is considered rude, disrespectful, or suspicious, so one thing children probably didn’t do was ask adults to teach them, though they may have asked other children.)
Though we no longer live on the savannah, and most of us couldn’t survive there if we tried, we still have these evolved tools for learning our culture and our environment. That means that we can’t not learn. Learning is built into us, and children are especially keen and capable learners.
But in my experience, this is not the answer people are looking for, because it doesn’t answer the real question: "How will my child learn the right things without a required curriculum and formal instruction?"
What are the right things? No, really, stop and think about this. Who decides what the "right things" are? How many of the supposedly critical skills you learned in school are actually relevant to your life? How much “crucial knowledge” do you vaguely remember once having lessons on, but couldn’t possibly recall now?
We are built to learn the culture around us, and to keep learning and adapting throughout our lives (though never as well as when we are young). The truly necessary skills, the ones that everyone around us use every day, we will learn. If no one interferes, we will want to know how to read, how to write, how to use a computer, how to participate in the kinds of conversations our community has, how to cook, how to navigate safely in a car-heavy city, and how to tell jokes, just like our ancestors were driven to learn how to hunt, how to gather, how to stay safe around wild animals, how to get along in their group, and how to tell jokes. And so we will learn what we need to know, whether by observing, experimenting, or asking someone to teach us.
“Okay,” I hear you say, “but what about "college and career readiness"? There’s a lot you have to know to get into college and get a good job, even if it’s not relevant to being an adult.”
This is absolutely true. In the past hundred or so years, school has evolved into its own self-referential, internally structured beast, and doing well in school serves as a signal to others (especially employers) that you are a well-educated, competent, hard-working, and probably compliant individual. (See The Case Against Education for more on the idea of college as signaling). That means that there is value to “doing well” at schoolish things, even if the knowledge is useless.
But this fact does not justify overruling young people’s agency over their lives; it justifies giving them honest information. Young people are not stupid and they want their lives to work out. Most will willingly do what is necessary to live a meaningful and successful life, including study a lot of topics that they may or may not see as valuable, in order to get the outcomes they want. In my classrooms, I've always had available a child-friendly version of the local school standards, and talked honestly with the children about what these standards are, where they come from, and the pros and cons of paying attention to them. More often than not, the children come to me asking for lessons related to these standards, not the other way around.
Furthermore, most willing young people need far less time to learn everything in those standards than the usual pace would suggest. The standards are spread over 13 years with massive repetition not because it truly takes this long, but because schools are dragging children, often kicking and screaming, through a set curriculum, and this is a much more difficult process than teaching a child who wants to learn.
In fact, sometimes waiting can, by itself, lead to faster learning. In an experiment in 1929, L.P Benezet, who was the superintendent of the Manchester, New Hampshire school district, had several teachers stop teaching any math before the 7th grade, though he did give them informal math and logic problems to think about. (By the way, these classes in the poorest schools, as Benezet quite explicitly recognized that the wealthier parents would never tolerate such an experiment). Once these children began formal math instruction, they caught up to their peers in the district within a year.
When children are in charge of their own lives, have agency over their learning, and can make well thought-out decisions about their plans, they can figure out what they need to learn and learn it quickly, provided they have access to adults and resources to help them. That applies whether the learning is filling in academic gaps in order to apply to college, doing a deep dive into a research topic purely for pleasure, or learning new skills on the job.