Hallie Preskill and Rosalie Torres (1999) describe mental models as a set of personal opinions, perceptions, and views of the world. Developed over time, such values, beliefs, assumptions, and knowledge guide people in their everyday lives and are thought of as "truths." Mental models are powerful because they frame and influence the way educators and school districts perceive, understand, interpret, and act upon their world. However, not all mental models are functional or correct. Change requires that people unlearn negative mental models and learn new ones, and staff developers play a critical role in designing and delivering the kind of professional learning that can help educators do so. In this article, the author discusses how educators can unlearn dysfunctional or wrong mental models and learn new ones. Characteristics of both individual and organizational mental models are presented.