of books at home; Isaiah does beautifully on his reading test at school; this must be because his mother or father regu- larly reads to him. But Isaiahs 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 Emilys friend Ricky doesnt 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 doesnt have an im- pact 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 childs 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 theyre 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 dont say that books in the house cause high test scores; it says only that the two are correlated. How should this correlation be interpreted? Heres a likely theory: