Every morning before Cindy Price starts teaching her first graders in New Castle, Delaware, she fires up ClassDojo , a classroom communication app. She checks parent messages, finds out whether any students will be out sick and reads school news. When a child shows a trait like "amazing thinking" or "great listening," she adds a point to the student's avatar--a personalized cartoonish monster--generating a bright ping! that makes classmates perk up. Points come off for disruptive behavior. Twice a day, Price shares class photos or videos with parents. And during free time, she plays ClassDojo's short personal-growth videos, which use monsters like ClassDojo's excitable green mascot, Mojo, to teach lessons on empathy and perseverance. "It's helping teachers be successful in the classroom," she says. Teachers like it because teachers have shaped it, in the form of 20,000 who provide constant feedback. That bottom-up approach, and kid-friendly gamification, has given it penetration into 90% of U.S. schools, according to the company. "Why don't we just go to the people doing the work?" says CEO and cofounder Sam Chaudhary. "It sounds obvious, but it wasn't being done."