When we talk about school being a place to socialize kids, let's be clear that it's a place to socialize kids who like school. If you're an outcast, what you learn is that you don't fit in and that it's hopeless.
What I'm going to focus on is that kids who are popular at school are nicer than the other kids. Really. Studies show. Which means that if you want your kid to get those mysterious benefits of socialization, just teach the kid empathy.
But that's easier said than done. Because empathy starts to happen at birth, and it's well formed by age eight. And if we could teach empathy there would be no kids with Aspergers, because a large part of what plagues people with Aspergers is their lack of empathy. Empathy is not logical, so it has a hard time fitting in the Apergers brain. If we could teach empathy, we could teach it to kids with Aspergers.
But empathy is, in fact, simply a result of decent parenting very early in life for neurotypical kids, because they are hard-wired to learn empathy just by watching the reaction of adults.
So socialization is the process of learning by way of fitting in at school. And people who fit in at school are nicer than most of the other kids. So you no longer have to worry that your kid won't be socialized if you take the kid out of school. Just as Aspergers and intellectual cowboy are hard-wired at birth, so, too, is popularity. Whether or not your kid is in school.