Teacher preparation programs are in danger of seriously under-preparing elementary teachers to teach mathematics for understanding if they wait to provide students with evidence of effective mathematics teaching methods in the mathematics methods courses. With strong traditional beliefs about how mathematics ought to be taught and their determination to be able to explain mathematics to elementary children, the methods course is much too late to change preservice teachers' perceptions of mathematics or how to teach it. If we want to change the way they teach mathematics, we must do it in their mathematics content courses. In the content courses, we have a chance to provide them with positive and successful personal mathematics constructions. Only when they learn to become active problem-solvers, can they teach others the importance of interactive problem solving as a means of truly understanding mathematics. It is only through their own experience with mathematics that they can come to appreciate the value of a student-centered environment for learning and to appreciate how a teacher's desire for control can stifle true learning.