• Matters: The child’s parents speak English in the home.

• Doesn’t: The child’s parents regularly take him to museums.

A child with English-speaking parents does better in school than one whose parents don’t speak English. Again, not much of a surprise. This correlation is further supported by the performance of Hispanic students in the ECLS study. As a group, Hispanic students test poorly; they are also disproportionately likely to have non-English-speaking parents. (They do, however, tend to catch up with their peers in later grades.) So how about the opposite case: what if a mother and father are not only proficient in English but spend their weekends broadening their child’s cultural horizons by taking him to museums? Sorry. Culture cramming may be a foundational belief of obsessive parenting, but the ECLS data show no correlation between museum visits and test scores.

• Matters: The child is adopted.

• Doesn’t: The child is regularly spanked.

There is a strong correlation—a negative one—between adoption and school test scores. Why? Studies have shown that a child’s academic abilities are far more influenced by the IQs of his biological parents than the IQs of his adoptive parents, and mothers who give up their children for adoption tend to have significantly lower IQs than the people who are doing the adopting. There is another explanation for low-achieving adoptees which, though it may seem distasteful, jibes with the basic economic theory of self-interest: a woman who knows she will put her baby up for adoption may not take the same prenatal care as a woman who is keeping her baby. (Consider—at the risk of furthering the distasteful thinking—how you treat a car you own versus a car you are renting for the weekend.) But if an adopted child is prone to lower test scores, a spanked child is not. This may seem surprising—not because spanking itself is necessarily detrimental but because, conventionally speaking, spanking is considered an unenlightened practice. We might therefore assume that parents who spank are unenlightened in other ways. Perhaps that isn’t the case at all. Or perhaps there is a different spanking story to be told. Remember, the ECLS survey included direct interviews with the children’s parents. So a parent would have to sit knee to knee with a government researcher and admit to spanking his child. This would suggest that a parent who does so is either unenlightened or—more interestingly—congenitally honest. It may be that honesty is more important to good parenting than spanking is to bad parenting.

• Matters: The child’s parents are involved in the PTA.

• Doesn’t: The child frequently watches television.

A child whose parents are involved in the PTA tends to do well in school—which probably indicates that parents with a strong relationship to education get involved in the PTA, not that their PTA involvement somehow makes their children smarter. The ECLS data show no correlation, meanwhile, between a child’s test scores and the amount of television he watches. Despite the conventional wisdom, watching television apparently does not turn a child’s brain to mush. (In Finland, whose education system has been ranked the world’s best, most children do not begin school until age seven but have often learned to read on their own by watching American television with Finnish subtitles.) Nor, however, does using a computer at home turn a child into Einstein: the ECLS data show no correlation between computer use and school test scores.

Now for the final pair of factors:

• Matters: The child has many books in his home.

• Doesn’t: The child’s parents read to him nearly every day.

As noted earlier, a child with many books in his home has indeed been found to do well on school tests. But regularly reading to a child doesn’t affect test scores.

This would seem to present a riddle. It bounces us back to our original question: just how much, and in what ways, do parents really matter?

Let’s start with the positive correlation: books in the home equal higher test scores. Most people would look at this correlation and infer an obvious cause-and-effect relationship. To wit: a little boy named Isaiah has a lot of books at home; Isaiah does beautifully on his reading test at school; this must be because his mother or father regularly reads to him. But Isaiah’s friend Emily, who also has a lot of books in her home, practically never touches them. She would rather dress up her Bratz or watch cartoons. And Emily tests just as well as Isaiah. Meanwhile, Isaiah and Emily’s friend Ricky doesn’t have any books at home. But Ricky goes to the library every day with his mother; Ricky is a reading fiend. And yet he does worse on his school tests than either Emily or Isaiah.

What are we to make of this? If reading books doesn’t have an impact on early childhood test scores, could it be that the books’ mere physical presence in the house makes the children smarter? Do books perform some kind of magical osmosis on a child’s brain? If so, one might be tempted to simply deliver a truckload of books to every home that contains a preschooler.

That, in fact, is what the governor of Illinois tried to do. In early 2004, Governor Rod Blagojevich announced a plan to mail one book a month to every child in Illinois from the time they were born until they entered kindergarten. The plan would cost $26 million a year. But, Blagojevich argued, this was a vital intervention in a state where 40 percent of third graders read below their grade level. “When you own [books] and they’re yours,” he said, “and they just come as part of your life, all of that will contribute to a sense . . . that books should be part of your life.”

So all children born in Illinois would end up with a sixty-volume library by the time they entered school. Does this mean they would all perform better on their reading tests?

Probably not. (Although we may never know for sure: in the end, the Illinois legislature rejected the book plan.) After all, the ECLS data don’t say that books in the house cause high test scores; it says only that the two are correlated.

How should this correlation be interpreted? Here’s a likely theory: most parents who buy a lot of children’s books tend to be smart and well educated to begin with. (And they pass on their smarts and work ethic to their kids.) Or perhaps they care a great deal about education, and about their children in general. (Which means they create an environment that encourages and rewards learning.) Such parents may believe—as fervently as the governor of Illinois believed—that every children’s book is a talisman that leads to unfettered intelligence. But they are probably wrong. A book is in fact less a cause of intelligence than an indicator.

So what does all this have to say about the importance of parents in general? Consider again the eight ECLS factors that are correlated with school test scores:

• The child has highly educated parents.

• The child’s parents have high socioeconomic status.

• The child’s mother was thirty or older at the time of her first child’s birth.

• The child had low birthweight.

• The child’s parents speak English in the home.

• The child is adopted.

• The child’s parents are involved in the PTA.

• The child has many books in his home.

And the eight factors that are not:

• The child’s family is intact.

• The child’s parents recently moved into a better neighborhood.

• The child’s mother didn’t work between birth and kindergarten.