In India, where more than 250 million children have been affected by school closures, Worldreader is working with educational agencies and telecommunications companies to alert parents to its free e-reading service through WhatsApp and SMS group messages.

“The evidence is so overwhelming that without a literate and reading population, you can’t have a self-reliant, healthy population,” Mr. Risher said.

Other literacy organizations, nonprofits and subscription services have also opened up their e-book collections for children who are out of school. The digital reading platform Epic, which has more than 40,000 children’s e-books, has made its library available at no charge, allowing schoolteachers to give their students access to its e-books through June 30. Since the start of the pandemic, the nonprofit First Book has distributed more than a million print editions of children’s books, and has made downloadable e-books available to teachers to distribute to their students. In the past six weeks, teachers have used 724,000 download codes to access e-books for their students, surpassing the number of downloads for all of 2019, according to a spokeswoman for First Book. Scribd, an e-book and audiobook subscription service that includes 150,000 children’s and young adult titles, is offering free access to its digital library for 30 days. (One of the recommended reading lists is titled “Keeping kids busy at home.” “We’ve put together a list of kids’ books to help your household stay sane and even enjoy this time of forced family togetherness,” the description says.)

Worldreader remains focused on reaching children in the developing world, though they’ve discussed expanding to Europe and North America in the wake of school closures across those continents, Mr. Risher said, and the group’s BookSmart app is accessible in the United States and Britain.

Worldreader started with a trial program with e-readers in Africa in 2009, but a few years later the group shifted its focus to a mobile reading app for cellphones. Through partnerships with 426 different publishers, Worldreader built up a library of more than 12,000 e-books in more than 50 languages, including classics like “The Chronicles of Narnia” and contemporary best sellers like Mary Osborne’s “Magic Tree House” series and several of Neil Gaiman’s books for young readers. Penguin Random House has provided some 450 e-books for Worldreader’s library; Simon & Schuster has made 100 of its titles available, and plans to add another 100 books for the BookSmart app.

“They have been very assiduous about identifying the communities that need these books,” said Carolyn Reidy, the president and chief executive of Simon & Schuster. “Everyone’s at home, and everybody does not have the ability to do distance learning.”