America's most popular teacher doesn't work at Harvard University or a fancy prep school. In fact, he doesn't work in a school at all, but his lessons have been viewed more than 56 million times. Salman Khan, a former hedge fund manager, is the founder of Khan Academy, a free online learning platform with a library of more than 2,300 videos covering everything from basic algebra and differential equations to the Vietnam War.
In 2004, Khan's younger cousin in New Orleans, Nadia, was having trouble in her math class. Khan, an MIT graduate who was working in New York City, began tutoring Nadia over Yahoo! Messenger. Soon, more relatives began asking for help, so he started making YouTube videos explaining different topics, which they could view when they had time. Eventually, other people discovered his videos and thought they were useful.
Most videos are brief--anywhere from a couple of minutes to a half hour, depending on the subject. Khan scrawls equations and writes down key terms on a computer program that simulates a chalk board as he explains them with a voiceover track.
"Students were telling me they got better feedback on YouTube than in person with their teachers," he says. "The topics kept growing, [and] the feedback from users kept growing."
[Learn how college professors are taking advantage of YouTube.]
User feedback was so positive that in 2007 he founded the not-for-profit Khan Academy, which initially consisted of little more than a landing page for his videos. Today, the Academy features the videos, online exercises and assessments, and progress-tracking tools.
By 2009, Khan was making enough money through the YouTube partner program, which pays more than 20,000 of the site's top video creators a portion of ad revenue, to quit his job at Wohl Capital Management, a small hedge fund management firm, and focus on the Academy full time.
"It was kind of a leap of faith," he says. "Seven or eight months later, we got donors and I was able to pay myself a salary and translate the videos into 10 languages." So far, videos are being translated into Spanish, French, Russian, Hindi-Urdu, Mandarin, and more.
One of his donors just happened to be one of the most important men in the world: Bill Gates. The Bill & Melinda Gates Foundation made a $1.5 million donation to the Academy, and Google donated another $2 million.
"I see Sal Khan as a pioneer in an overall movement to use technology to let more and more people learn things," Gates says in a video posted on the homepage of the Khan Academy website. "It's the start of a revolution."
[Read more about Bill Gates's favorite tutor.]
Khan has already gained traction in some brick-and-mortal schools around the country. Two fifth grade and two seventh grade classes in the Los Altos school district in California are using the Khan Academy as part of a pilot program to test its effectiveness in school math classes. In the pilot, students watch his videos at home so that teachers act more like coaches who help individual students as they complete practice problems in class, rather than lecturing to all students at once. Khan hopes that, in the future, most classes will operate in this fashion. He estimates more than 1,000 K-12 teachers are already using his videos in some capacity in their classrooms.
He's still recording about three videos a day. While the Academy started with Khan's strengths--math and science--he's expanded to history, astronomy,, and economics. Students can also prepare for the SAT math section and GMAT exam. He's even hired a few more teachers to help him expand faster.
"Over the next five years, I think it'll be safe to say that we'll have done videos on all of K-12 and a lot of university topics, like computer science [and] electrical engineering," he says. "There's an infinite amount of stuff out there."
A math whiz, Khan was able to do most of the videos in that subject based on his memory, but he often gives himself a refresher course on, say, the French Revolution or the parts of a cell.
"I learn and immerse myself in the material," he says. If viewers don't understand the lesson, he'll redo it more clearly. The user feedback is "a key part of it. If I do a video that's confusing, we'll redo the video," Khan notes.
Khan's videos continue to grow in popularity. They are viewed more than 2 million times a month by students struggling with homework, teachers looking to simplify their explanations, and curious people who want to learn. "We're trying to educate the world," he says in his introduction video. "I want it to be the operating system for everything that goes on in the classroom."
See how your school stacks up in our rankings of Best High Schools. Have something of interest to share? Send your news to us at highschoolnotes@usnews.com.
