"This," says Matthew Carpenter, "is my favorite exercise." I peer over his shoulder at his laptop screen to see the math problem the fifth grader is pondering. It's an inverse trigonometric function: ...

The headquarters of what has rapidly become the largest school in the world, at 10 million students strong, is stuffed into a few large communal rooms in a decaying 1960s office building hard by the ...

Before he started the most popular education site on the Web, Salman Khan was neither an educator nor an entrepreneur. His outsider status helps explain why he's been able to solve a problem that ...