This dissertation provides insights into the potential for the Next Generation Science Standards (NGSS) and a complementary instructional model, transdisciplinary STEM, to advance constructivist approaches to high-quality education by providing a framework and pedagogical model that authentically communicate these principles for practitioners. Through two research projects, I explore some of the dilemmas facing educators implementing these reform initiatives. First, I present a study of the relationship between discursive epistemic agency and scientific authenticity in school. I argue that epistemological misalignment between perspectives underpinning traditional approaches to school science and those of professional science contribute to tensions regarding the amount of control that students should be given over the discourse of science. Using NGSS as representative of authenticity, I explore and respond to a dilemma faced by many science educators of whether students must relinquish discursive agency for their participation in science to be considered authentic. Analyses of contrasting types of ‘talk’ in a first-grade classroom support the theoretical argument that increased discursive agency directly contributes to engagement in authentic science practices (as defined by NGSS). The second report represents a case study analysis of the perspectives of participants in a degree program focused on interdisciplinary approaches to learning. I ask, how do teachers’ epistemological beliefs affect their perceptions of the locus of perceived barriers and the extent to which those barriers may be overcome? My results indicate that accessing teacher beliefs is productive for understanding the relative alignment between their personal epistemologies and those of the reform. Furthermore, epistemological beliefs may be intimately entangled with, rather than function discretely from, these teachers’ perceptions of constraints to implementation of reform. The conclusions of these two research projects indicate that epistemological perspectives pervade the discourse of science, the text of curricular resources, and the language teachers use to talk about the implementation of pedagogical models. Furthermore, authentic enactments of science and meaningful learning are at least partially dependent upon a consistent alignment between the epistemologies underpinning reform efforts, those reflected in the language of school, and the personal epistemologies of educators.