By 2019, half of all courses in grades 9-12 will be delivered online, according to Enrollment in online classes, according to the Hoover Institute at Stanford University. But for data closer to today, "enrollment in online classes last year reached the 1 million mark, growing 22 times the level seen in 2000," the Christian Science Monitor reports, citing figures from the North American Council for Online Learning. The efficiency of distance learning, the low cost of delivering, and its flexibility for students who do better outside of conventional school are reasons cited for its rapid growth. Of course, states are all over the map in what they allow and require. Check out the article for details and note the views of professor Luis Huerta at Columbia University and researcher David Reed at Arizona State University.