The current issue of Education Week has a long story on “learning time” and one of the studies cited makes a far-reaching claim. It has to do with the “summer effect,” that is, the extent to which learning gains made during the school year slip away during the summer months. When the school year ends, if students don’t pursue activities that support the studies and exercises they carried out in class, the learning doesn’t stick.

The shift especially hits certain populations. Here’s the estimate: “The researchers calculate that, by the time students reach ninth grade, two-thirds of the achievement gap between disadvantaged and better-off students owes directly to that so-called ‘summer learning loss.’”

That makes leisure time a daunting factor in academic achievement and in the achievement gaps that continue to plague the schools. It throws a shadow over the power of schools to close the gaps on their own, and it forces educators to do something most are entirely uncomfortable doing: casting a judgment on the home life and culture of students and students’ parents.

The article skirts that judgment by identifying “disadvantage” entirely with class, not with culture at all. Disadvantaged students “lost important ground over the summer months,” it says, “presumably because they have fewer opportunities to go to camp, travel, buy books, or take part in other enrichment activities.”

We won’t downplay the role of money in the advantage, but we should also note that one of the cheapest kinds of culture to create in youngsters’ leisure hours is a reading culture. Public libraries are everywhere (the nation gained more than 300 of them in the last 10 years), and the books are free. Every Barnes & Noble and Borders hosts “story time” for kids two or three days a week. Used bookstores and thrift stores stock paperbacks for 50 cents.

We should remember, too, that one of the surest determinants of academic success is the amount and quality of reading material in the home. Some researchers have, in fact, pegged it as a better determinant than income level. In other words, a lower-middle-class kid from a text-rich home has a higher probablility of success than a middle-class kid from a text-poor home. They also find that a child who is read to by parents arrives at kindergarten with a vocabulary of up to 8,000 words, while a child who is not read to by parents can arrive with a vocabulary of 2,000 words.

Can the teacher fix this? Not much. In fact, the vocabulary gap usually grows.