That's all as it should be. Like our cars, our children don't exist in a vacuum. They're going to drive the same roads and live in the same society as we do. So we all share an interest in what they study, absorb, and know.
That's why most states - including Pennsylvania - require annual portfolios from homeschooled kids. Many also mandate periodic standardized testing or other academic assessments of these children.
But New Jersey is one of 11 states where homeschooled children aren't monitored at all. That included Christiana Glenn, the 8-year-old North Jersey girl who died earlier this year of complications from an untreated broken leg. Her mother had never enrolled any of her three children in school, nor had state educational authorities checked up on them. State law didn't require them to.
Back in 2003, the discovery of four starving brothers in Collingswood prompted similar calls for closer examination of homeschooled kids in New Jersey. One of the boys was found eating from a neighbor's garbage can - an enduring and sickening image.
While tragedies of this sort get all the ink, they're actually the weakest argument for stronger regulation of homeschooling families. As some of these families have correctly noted, state agencies are already responsible for child safety. If New Jersey's Division of Youth and Family Services had been doing its job, Christiana Glenn might still be alive.
But we would still have to worry about the quality of homeschooled children's education, which is not the responsibility of DYFS.
That's why reformers like Horace Mann established "common schools" in the first place, back in the 1830s and 1840s: to ensure that every American could read and write, and to promote unity across the nation's many differences. "If this education should be universal and complete," Mann wrote of public schools, "it would do more than all things else to obliterate distinctions in society."
Ironically, Mann's wife, Mary, taught their three children at home; like many other Americans then and since, Mann did not trust the schools to provide a proper education for his children. Nor could anyone today seriously maintain that public schools have made our society more equitable; rather, they have widened the gap between haves and have-nots.
Furthermore, as the Supreme Court declared in Pierce v. Society of Sisters (1925), "the child is not the mere creature of the state." Homeschoolers love to cite this decision, which found that states could not require kids to go to public schools, or prohibit them from attending private ones.
But the same decision emphasized that the state can and should "inspect, supervise, and examine" all education, no matter where it takes place. That's why private schools must conform to state regulations on curriculum, number of school days, and much else.
So why exempt homeschooled kids? I'm not suggesting any draconian scheme of government snoops descending on families to make sure they're reading Shakespeare. But we shouldn't leave homeschoolers entirely alone to teach whatever and however they wish.
We should instead take a closer look at homeschooling, an enormous social trend that still escapes serious public attention. In 1985, an estimated 50,000 kids were homeschooled; today, about two million are. That means more kids are homeschooled than are attending charter schools, which have been the subject of a popular movie - last year's Waiting for "Superman" - and countless books and articles.
Don't think the homeschoolers are all crunchy hippies or conservative, white evangelicals, either. Their ranks include Muslims, Jews, and Catholics, as well as blacks, Hispanics, and Asians. They also include well-to-do families who hire high-priced tutors, with annual fees rivaling the cost of tony private schools.
But in New Jersey and 10 other states, we really don't know what they're up to. And we should.
It's not that homeschooled kids need protection from their ne'er-do-well parents, which is all you ever read about in the papers. But, as with auto inspections, we need to make sure they have a few educational elements in common with the rest of us. How else will they learn to share the road?
Jonathan Zimmerman is a professor of history and education at New York University and the author of "Small Wonder: The Little Red Schoolhouse in History and Memory" (Yale University Press). He can be reached at firstname.lastname@example.org.