When Paul Edelman was working as a middle school teacher in New York City during the early '00s, his school gave him none of the lesson plans, handouts, and workbooks necessary for running a classroom. "When school ended at 3 p.m., it was really just the beginning of my workday," says Edelman. He says his first year was "brutal," and his second and third years were only marginally better.

Edelman's experience is hardly unique; many young teachers burn out in part because their schools expect them to generate all of their own materials. "I cried every night," says former teacher Amy Berner. "Every night you sit down and think, 'I am completely unprepared for tomorrow.'"

Out of such pain came an idea: "What if we could create a vast repository of resources that already worked for other teachers," he asks, "juiced with free market forces?"

In 2006, Edelman started Teachers Pay Teachers, an online marketplace for educators to sell digital copies of their classroom materials to each other for small amounts of money. "It's booming," says Berner, the company's head of community and editorial. Gross sales ballooned from $900,000 in 2010 to $44 million in 2013, and so far teachers have earned nearly $48 million on the site. There are more than one million products to choose from, including lesson plans, worksheets, flash cards, PowerPoint presentations, games, quizzes, graphic organizers, bulletin board ideas, and parent guides. And the materials are built by real teachers, so they tend to be perfectly tailored to classroom use.

Edelman says that requiring educators to produce their own classroom materials has its benefits. "I like that teachers in the U.S. have the freedom to create and teach the way they teach best," he says. Despite feeling overworked and underprepared, Edelman says that he was still grateful as a teacher not to have "a nationalized and controlled curriculum," as many other countries do. Teachers Pay Teachers offers the best of both worlds because educators don't have to spend all their free time generating materials from scratch, but they still get to pick what's best for their students—and can tailor the material however they see fit.

For teachers, whose compensation generally reflects not their talent and drive but the number of years they've served in the classroom, Teachers Pay Teachers brings a refreshing dose of market incentives. More than 1,300 teachers have earned at least $5,000 selling their materials through the company, and 164 have earned more than $50,000.

The site's breakout star and top seller is a kindergarten teacher in Macon, Georgia, named Deanna Jump. By selling activities and lesson plans, such as Guided Reading 101: Printables, Strategies and Word Work ($8) and Insects Math and Literacy Fun ($6.80), along with 145 other products, Jump has earned more than $2 million on Teachers Pay Teachers. With her wholesome good looks and exceptional talent as a teacher and curriculum author, Jump makes for an ideal public face. And she hasn't changed with her newfound wealth: Jump still teaches, and the first thing she did after the money started rolling in was purchase a handicap-accessible van for her quadriplegic brother.

At a time when teachers are being judged by central bureaucracies based on how their students perform on high-stakes tests, and union contracts enforce absurd work rules and lockstep pay increases, Teachers Pay Teachers offers educators the dignity of being treated like professionals. "It's like, 'I'm actually being respected for the expert that I am,'" says Berner. "Calling it a revolution in education I don't think is overstating it."