Three years ago, Clintondale High School, just north of Detroit, became a flipped school" - one where students watch teachers' lectures at home and do what we'd otherwise call "homework" in class. Teachers record video lessons, which students watch on their smartphones, home computers or at lunch in the school's tech lab. In class, they do projects, exercises or lab experiments in small groups while the teacher circulates. In the fall of 2011, Clintondale flipped completely - every grade, every class. "On average we approximated a 30 percent failure rate," said Green. "With flipping, it dropped to under 10 percent." Graduation rates rose dramatically, and are now over 90 percent. College attendance went from 63 percent in 2010 to 80 percent in 2012. Flipping also changes the distribution of teacher time. In a traditional class, the teacher engages with the students who ask questions - but it's those who don't ask who tend to need the most attention. The biggest effect of flipping classrooms is on the students at the bottom. "It's tough to fail a flipped class, because you're doing the stuff in here," said Rob Dameron, the head of the English department. "I used to have about a 30 percent failure rate in English. Now, out of 130 kids, I have three who are failing - mostly due to attendance problems." Flipped classrooms require more creativity and energy from the teacher. "Lots of teachers who aren't really good teachers are resistant to this - they like to build time into the day when kids are working to do their taxes or catch up on email.".