Just a couple of miles north of Anacostia, for example, in the borderline Washington neighborhood known as Capitol Hill, Neuman and Moland found more than 2,000 children’s print resources in stores—i.e., a book for every two kids. While still equipped with relatively few reading resources, the borderline neighborhoods the researchers studied, overall, had 16 times as many books as their high-poverty counterparts.

Equating access to books with access to stores that sell books is hardly perfect, but it makes a good deal of sense when considering the existing data on the book habits and day-to-day realities of low-income families. Statistically, poor families are far less likely to utilize public libraries, whether it’s because they’re not acclimated to using them or because they’re worried about being charged late fines, or because they’re skeptical of putting their name on a card associated with a government entity. Neuman has found that only 8 percent of such families report they have taken advantage of library resources.

Meanwhile, even though parents could in theory easily order books for their kids from online stores like Amazon, a perhaps surprising percentage of low-income families lack access to high-speed internet at home—a little over half of those with children under 8, according to a 2013 study. And only 61 percent of poor families with young children, according to the same study, have internet-enabled mobile devices. That means the presence of brick-and-mortar stores where books are sold can be critical, especially during the summer months when poor children aren’t in school and lose many of the academic skills they developed over the previous year.

As with exposure to vocabulary, access to books can have both immediate and longer-term impacts on a child’s academic and socioeconomic outcomes. Living in a book desert “may seriously constrain young children’s opportunities to come to school ‘ready to learn,’” Neuman and Moland write. A lack of access to books may help explain why, according to some research, children from economically disadvantaged communities score 60 percent lower on kindergarten-readiness tests that assess kids’ familiarity with knowledge as basic as sounds, colors, and numbers. And researchers say living in a book desert in one’s early years can have psychological ripple effects: “When there are no books, or when there are so few that choice is not an option, book reading becomes an occasion and not a routine,” they write.

According to Neuman, who, as the assistant education secretary under Bush, was in charge of implementing No Child Left Behind, the stalled achievement rates of the country’s children show that more emphasis needs to be placed on what happens in their lives outside of schools. “We have seen that No Child Left Behind was an effort to really improve schools while ignoring parent education,” she said. “What we realize is that children are out of school more than they’re in it.” Contrary to the conventional assumption that academic interventions can only happen in school, she continued, some of the most critical factors in kids’ achievement involve family and environment.