Mac Barnett and Jory John, coauthors of The Terrible Two (Abrams/Amulet), are pranksters with a purpose. Rather than playing tricks on unsuspecting booksellers to promote their middle-grade release, like they did at the fall regionals, the duo want to talk about something just as near and dear to their hearts: how and where they met.

“The only reason Jory and I are working together now is because of 826 [Valencia],” Barnett says, referring to the educational nonprofit organization founded in San Francisco’s Mission District in 2002 by author Dave Eggers and teacher Nínive Calegari. Barnett and John met there in the summer of 2004: it was Barnett’s first day interning at Eggers’s publishing venture, McSweeney’s, and John’s first day interning at 826 Valencia. Their friendship flourished while collaborating on projects at work and was cemented by bingeing on television at each other’s homes.

The organization provides writing instruction for students from ages six to 18 in a neighborhood that is predominantly made up of low-income immigrants; it has spawned six chapters in half a dozen urban centers in the past decade. The army of 1,500 volunteer tutors at 826 Valencia include authors, editors, teachers, and professors. Programming includes after-school tutoring sessions, as well as more ambitious projects, such as writing-oriented field trips and book production clinics.

“Kids can come in and make a book in two hours,” says John, who worked there as program director after his internship. “That’s a class that’s booked a year in advance, it’s so popular.”

Volunteers also make forays into local schools, where projects include a semester-long workshop during which students produce a professionally bound book that is then distributed to local bookstores to sell. “It’s a really magical experience for a kid, that they can walk into a bookstore and see their essay or their story in a book on the shelf,” John says.

“In a big way, I feel like I got my start at 826,” notes John, who has written or coauthored half a dozen children’s books and edited Thanks and Have Fun Running the Country: Kids’ Letters to President Obama. His sentiments are echoed by Barnett, author of 20 books for children, including Extra Yarn, illustrated by Jon Klassen, a 2013 Caldecott Honor book, and Sam & Dave Dig a Hole, also illustrated by Klassen, a 2015 Caldecott Honor book. “I got my start teaching kids at 826, and I love teaching kids,” Barnett says. Although both are full-time authors (and pranksters) now, they still volunteer at 826.

Barnett and John note that the success of 826 Valencia—and its offshoots—is similar to the reason that indie bookstores are indispensable to their communities: 826 serves as a “third place,” a space that is neither home nor work.

Referring to the Pirate Supply Store on the ground floor of 826 Valencia, to fulfill the building’s zoning requirements for retail, as well as the Time Travel Mart at 826 in Los Angeles, Barnett adds, “If you’re visiting San Francisco and need a peg leg, or if you’re in L.A. and want a robot toupee, you can find them at 826 Valencia or at 826LA. These stores are great places to visit, and your purchase supports our programming.”

Although the Pirate Supply Store is a definite draw and pulls in customers from all over, what matters most to Barnett and John is the niche that 826 Valencia fills in the neighborhood. “Everyone is welcome at 826,” John says, “whether you are a kid who needs help with your homework, or you want to come in and help tutor, or you are coming to an event at night. We’re really good at creating programming that has value to the community.”