In the tale of "Stone Soup," a stranger vows to make soup for everyone in a village using only a stone--and convinces everyone in town to throw an ingredient into the stewpot. Schools that need to improve teacher practice quickly can also make stone soup, the author says, by harnessing the power of well-prepared teacher leaders to sharpen the classroom skills of those they coach. When teachers coach teachers, focusing each week on one "bite-sized," measurable teaching action to observe and sharpen, teacher improvement happens faster than with traditional approaches that try to evaluate and fix all aspects of teacher practice at once. Bambrick-Santoyo, managing director of Uncommon Schools-North Star charter schools, describes how principals at those schools delegate instructional coaching to chosen teacher leaders. They also give those leaders constant preparation and practice, through role-playing with them the dialogues and feedback sessions they plan to engage in with those colleagues they are coaching.