This dissertation represents original, independent research that is a contribution of new knowledge to the field of educational practice. As a new phenomenon in the California public school system, transitional kindergarten (TK) is now bringing about a closer look by researchers at legislative practices, TK program implementation, local school district policies, teacher preparation, and teacher implementation of best practices related to the education of children of approximately four years of age. The purpose of conducting this study was to broadly examine these topics, but more specifically, investigate the problem of children being assigned to teachers who do not have the knowledge and skills to implement developmentally appropriate practice (DAP). Methodologically, interviews with teachers currently assigned to TK classrooms in local education agencies (LEAs which are also referred to as “school districts”), provided numerous data sets regarding teacher preparation, institute of higher education (IHE) responsibilities, LEA policies and practices, teacher knowledge about DAP, evidence of implementation of both DAP and developmentally inappropriate practice (DIP), classroom environments, and other challenges. Results from this study indicate that many California children in TK classrooms are receiving instruction which is not developmentally appropriate. Ineffective or inappropriate teaching at any level can negatively impact academic and social-emotional growth. Closer examination of these potential implications could indicate the need for additional study, policy changes, and mitigation of adverse, albeit, unexpected consequences of TK legislation.