Kopp's Teach for America sticks recent college grads in crummy public schools in an effort to improve the American educational system.

Kopp came up with the idea for Teach for America—a Peace Corps-style program to bring teachers to poor schools—while she was an undergrad at Princeton. She made the idea her senior thesis; a year later, in 1990, she set about making it a reality. More than two decades later, Teach for America continues to place idealistic 20-somethings (often freshly minted undergrads) in America's lousiest schools for two years. It now has thousands of teachers deployed across the world, with Teach For All extending the program internationally. Teach for America has been widely praised for creating a culture of public service but it's had its share of critics, too. Some say the program is elitist and that its mainly middle-class teachers aren't prepared to deal with the challenges of inner-city schools. [Image via Getty]