For more than a century the American education system has been guided by the Industrial Age world view (the controlling paradigm) that delivers education services to children by teaching them in groups, by requiring them to learn a fixed amount of content in a fixed amount of time, and by having their teachers serve as center stage directors of their learning (the mental models supporting the paradigm). This paradigm and its allied mental models are stubbornly resistant to change. Yet, there is an inescapable consequence of this world view: It leaves some children behind. This world view is often called the Industrial Age Paradigm of education, and there is a growing movement in the United States to displace this world view by replacing it with a world view of teaching and learning better suited to the demands of our 21st Century society. The new paradigm is sometimes called the Knowledge Age paradigm of teaching and learning. More commonly it is referred to as the learner-centered paradigm. This paradigm is built on the heart-felt belief that each student is one child with one mind who deserves a learning experience that is tailored to his or her personal learning needs, interests, and abilities so that he or she can achieve required standards of learning and become a successful and productive citizen in society. Creating this kind of paradigm-shift, however, is so challenging that it is quite a bit like trying to get an entire religious community to convert to a new religion. Duffy has written this article for those who have an interest in creating paradigm shattering changes in American school systems. It is divided into three parts, and contains the following: (1) Part 1: Paradigms, Mental Models, and Mindsets In-Use; (2) Part 2: Why Mental Models Are Difficult to Change; and (3) Part 3: Behavioral Strategies and Observable Behaviors.