ratio between prep time and teaching time in the Shanghai schools we visited. In the U.S., she said, teachers typically have one hour to prepare for five classes. In the Shanghai schools, they have four hours to prepare for two hours of teaching. This, she said, makes all the difference. Teachers can use this time to collaborate with other teachers to craft great lessons, to talk with other teachers about particular students' learning needs and how they might work together to address them, or to do the research needed to get ready to do another improvement project.