Remember when summer was a delicious three-month break from reading, writing and math? Now it’s more likely seen as that period between school years in which too many kids forget too much of what they just spent months learning.

There’s even a name for it — “summer learning loss” — but it doesn’t affect all students in the same way, even if this phenomenon has been made out to be broadly based.

Middle-class students actually see learning gains over the summer, according to Johns Hopkins researchers, while students from low-income families see a significant slide, concentrating the problem on poor children.

Approximately two-thirds of the ninth-grade achievement gap between disadvantaged students and others is said to be the result of summer learning loss during elementary school, according to Johns Hopkins researcher Karl Alexander. And, according to this 2011 Rand report, “Making Summer Count: How Summer Programs Can Boost Children’s Learning”:

“Most disturbing is that summer learning loss is cumulative; over time, the difference between the summer learning rates of low-income and higher-income students contributes substantially to the achievement gap.

This makes sense, given that children who aren’t poor have a range of options — camp, travel programs, internships, etc. — from which they can learn in non-academic settings. Social scientist Gerald Bracey wrote in 2009:

“Even organized sports teach children about mathematics, rules, teamwork, planning, and so on. Likewise, a family game like Scrabble is about linguistics, psychology, mathematics, memory, competition, and doggedness. It’s about mastering the rules. In short, middle class children experience many growth opportunities not available to most poor children.”

Though 100 years of research bears out the reality of the loss — at least when it comes to kids who live in poverty — what to do about it is less obvious than it might seem.

If summer, for example, is a time of forgetting, year-round schooling seems like an appropriate solution. Not necessarily. Results for this approach are decidedly mixed, at least in terms of standardized test scores, which is how learning loss is measured.

Summer school is a perennial favorite approach to stem summer learning loss, but results depend on a combination of factors, including the program’s quality and the willingness of the student to learn. Many financially strapped school districts don’t have the resources to address the summer needs of students who are far behind. In D.C. public schools, for example, the five-week summer program this year was designed for struggling readers but not for students who are profoundly behind.

Researchers, in fact, have found that summer academic programs are more effective — based on test scores — for students who are not economically disadvantaged. What this suggests is that programs for kids who aren’t poor are better constructed and resourced.

So what works?

For the children who need it most — poor children — well-thought programs provide broader-based support, but one intervention that has proved to work well in stemming reading loss is ensuring that young people have books to read.

Library reading programs work — but for many kids in big cities, getting to a library can be impossible. The key, according to experts such as Richard Allington, a researcher at the University of Tennessee at Knoxville, is making sure that children have access to books they want to read. Book giveaways work.

There are all kinds of resources available — on and off the Internet — to help parents give their children enriching summers. It is the children of parents who don’t know how to find those resources who are most severely affected by summer learning loss.