Jeff Sandefer is an entrepreneur and socratic teacher. He started his first company at 16, and his latest venture grew to several billion dollars in assets. The Economist magazine named him one of the world’s top 15 business school professors. Now, he’s a full-time teacher at Acton Academy, a cutting-edge K-12 school whose one-room school house for the 21-century model is spreading across the globe, with over 80 affiliates and over 8,000 applications from parent entrepreneurs who want to launch a school.