"Over the past few decades, organizations, researchers, and professional developers have noted the potential for using classroom discussions to improve student learning in mathematics classrooms. Yet, for teachers, managing the often-competing demands that arise while attempting to plan for and enact these discussions can be challenging. To better understand these challenges, this dissertation describes the results of a study characterizing the instructional decision-making of three experienced middle-grades mathematics teachers as they encountered instructional dilemmas while planning for and enacting collaborative mathematics discussions. To study decision-making, I observed teachers across several lessons, interviewed them after lessons, and analyzed lesson plans. Studying decision-making as it appeared in teachers' lived classroom experiences provided an authentic and situated perspective on the complexities of their decision-making. In order to analyze their decisions, I attended to teachers' instructional goals, which consisted of lesson-specific content goals, broad content goals, mathematical practice goals, and goals for establishing a mathematical community. Additionally, I used Herbst & Chazan's (2011) theory of professional obligations to understand why teachers made certain decisions based on their goals, consistent patterns of instruction, and the particular dilemmas they encountered. This theory argues that teachers' decisions are a function of their obligations as representatives of the discipline of mathematics, in developing students as individuals, in mediating productive interaction between students, and as representatives of the school as an institution. The main finding of this study was that all three teachers' decision-making was largely explained via their primary professional obligation - with important limitations. Along with this main finding, there were three subfindings. First, teachers' decision-making was largely explained via their primary orientation to their professional obligations. Second, all three teachers encountered scenarios in which they made decisions that deviated from their primary orientation to the professional obligations. Third, even though the teachers were experienced, used instructional resources (e.g., written curriculum materials) that supported implementing whole-class discussions, and were generally oriented philosophically with the importance of using discussions, this was not sufficient to avoid challenges one might expect to see while facilitating whole-class discussions. Most importantly, the types of challenges they encountered were, by-and-large, independent of the teachers and the nature of their dilemmas (i.e., how the dilemma was a conflict between two types of goals). Understanding how the nature of a teacher's decision-making is influenced by attending to their professional obligations during instructional dilemmas contributes to multiple areas of mathematics education. First, this study contributes to the research on teacher decision-making by expanding teacher decision-making to include many more contributing factors beyond content-focused decisions. Second, this study contributes to the research on whole-class discussions by considering teachers' orientations (via their professional obligations) as a confounding variable in the nature of their decisions influencing the discussion. Third, this study contributes to professional development and teacher education by better understanding how teachers' professional obligations can influence the opportunities students have to learn mathematics via their interaction during whole-class discussions."--Pages ii-iii.
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