Many preservice teacher (PST) programs throughout the world are preparing students to implement the Core Standards, which require deeper conceptual understandings of mathematics and an informed approach for teaching. In this qualitative multi-case study, researchers explored the teaching methods for two university instructors and changes in PSTs beliefs previously formed by personal elementary experiences. Results of the pre- and postcourse analysis demonstrate notable shifts in beliefs, understandings, and personal philosophies. A situated context and a social constructivist approach coupled with critical reflective exercises created an environment for PSTs to reflect upon and change their personal conceptual frameworks.