The student-teacher faces a rowdy class. “We’re not going to have that kind of behavior in here,” she says. “It’s too loud in here to move on.” The students don’t pay much attention. A boy in the back row, wearing a sleeveless T-shirt, slumps his shoulders. Another student waves his hand aimlessly. “Nah, just stretching,” he replies, when the teacher asks if he needs something. Scenes such as that aren’t uncommon in urban classrooms, but in this case there is one critical difference: These students are avatars—computer-generated characters whose movements and speech are controlled by a professional actor. Each of the five characters—all with distinct abilities, personalities, and psychological profiles, and even names like “Maria” and “Marcus”—were created as part of the TeachME initiative at the University of Central Florida, in Orlando. There, teacher-candidates can practice in a virtual classroom before ever entering a real one. Real-time classroom simulations like TeachME, supporters say, offer promise for a host of teacher-training applications. Through them, candidates could learn to work with different groups of students, or practice a discrete skill such as classroom management. Most of all, such simulations give teachers in training the ability to experiment—and make mistakes—without the worry of doing harm to an actual child’s learning. “It allows the teacher to fail in a safe environment,” said Lisa Dieker, a professor of education at the University of Central Florida and one of the designers of TeachME. “Real kids, trust me, will remember in May what you said to them in August. You can’t reset children.”