This study examines how, if at all, multiple subjects and administrative services credential preparation programs are changing in response to California's newest grade, Transitional Kindergarten (TK). We analyzed interviews from university faculty in early childhood education and credential programs in five institutions of higher education and collected survey data from early childhood professionals across 16 counties in the state. We describe gaps in knowledge about early childhood and developmental science needed to work with children in effective and developmentally responsive and appropriate ways. The study informs a much needed conversation about the consequences of implementing TK as a stand alone change rather than part of a comprehensive coordinated systems level reform.