HOW THE KHAN ACADEMY is changing the rules of education.

The videos are decidedly lo-fi, even crude: Generally seven to 14 minutes long, they consist of a voice-over by Khan describing a mathematical concept or explaining how to solve a problem while his hand-scribbled formulas and diagrams appear onscreen. Like the Wizard of Oz, Khan never steps from behind the curtain to appear in a video himself; it’s just Khan’s voice and some scrawly equations. In addition to these videos, the website offers software that generates practice problems and rewards good performance with videogame-like badges—for answering a “streak” of questions correctly, say, or mastering a series of algebra levels. (Carpenter has acquired 52 Earth badges in math, which require hours of toil to attain and at which his classmates gaze with envy and awe.)

Initially, Thordarson thought Khan Academy would merely be a helpful supplement to her normal instruction. But it quickly become far more than that. She’s now on her way to “flipping” the way her class works. This involves replacing some of her lectures with Khan’s videos, which students can watch at home. Then, in class, they focus on working problem sets. The idea is to invert the normal rhythms of school, so that lectures are viewed on the kids’ own time and homework is done at school. It sounds weird, Thordarson admits, but this flipping makes sense when you think about it. It’s when they’re doing homework that students are really grappling with a subject and are most likely to need someone to talk to. And now Thordarson can tell just when this grappling occurs: Khan Academy provides teachers with a dashboard application that lets her see the instant a student gets stuck.

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