Salman Khan was working as a hedge fund analyst when he started using online tools to tutor his cousins in math. Nine years later, his nonprofit organization, Khan Academy, draws on the same approach to offer more than 5,000 free, web-based video lessons to millions of students across the globe, disrupting not only schools but also the education industry built around them.

A version of this article appeared in the January–February 2014 issue of Harvard Business Review.