At last count, there were more than 1 million enrollments in K-12 online schools in the United States. And according to recent research, the number of students taking courses online will jump to more than 10 million in the next five years. But even with this rapid growth (up from zero enrollments in the mid-1990s), online education is only beginning to address the needs of American students. What’s standing in the way of even more widespread adoption? What have we learned so far in these early years? And can any of what we’ve learned be applied in traditional classrooms?