This study investigates 7th grade teachers' curricular reasoning and MKT in algebra and statistics. Although the use of curriculum materials and MKT both influence the quality of mathematics instruction, no relationship between teachers' curricular reasoning and MKT was found. Further, teachers' curricular reasoning across algebra and statistics was very similar despite differences in these fields and differences in MKT. A model for thinking about the knowledge needed to provide high quality instruction is proposed by considering the role of curricular reasoning and MKT in instruction.

Teachers' instructional decisions are important for students' mathematics learning as they determine the learning opportunities for all students. This study examines teachers' decisions about the activities and tasks they choose for students' mathematics learning, the ordering and connecting of mathematics topics, and the mathematics within curricula not to cover. These decisions are referred to as curricular decisions. I also identify teachers' mathematical schemes, referred to as mathematical meanings, in relation to geometric reflections and orientation of figures and examine teachers' reasoning with their mathematical meanings as they make these curricular decisions. Additionally, based on the results of this study I identify several productive and unproductive mathematical meanings in relation to geometric reflections and orientation of figures. Describing productive mathematical meanings as providing coherence to student mathematical understanding and preparing students for future mathematics learning (Thompson, 2016). These findings can be used to better understand why teachers make the curricular decisions they do as well as help teachers identify whether or not their mathematical meanings are productive in an effort to foster productive mathematical meanings for students.

For decades curriculum materials have been used as a means to reform the manner in which mathematics is taught. In an attempt to better understand what impact curriculum materials have on the teaching and learning of mathematics, researchers have begun to analyze the process in which teachers transform curriculum materials into instruction. Given that many of these studies have been broad in nature, I sought to study the specific decisions that three teachers made when planning lesson on geometric transformation and their reasoning for those decisions. In this study I found that while the participants in this study ignored the curriculum material I gave them as well as their district adopted materials in planning instruction, they made a wide variety of decisions with regards to other curriculum. In an attempt to describe this variety of decisions I expanded the previous methods of describing curriculum use decisions adding a self-create category as well as differentiating between the different types of adaptations teachers make. I also found that although teachers used different curriculum materials, they made similar decisions in how they planned the mathematics content of geometric transformations that seem problematic.

Researchers have found that teachers' decisions affect students' opportunity to learn. Prior researchers have investigated teachers' decisions while planning, implementing, or reflecting on lessons, but few researchers have studied teachers' decisions and their reasoning throughout the teaching process. It is important to study teachers' reasoning for why they make the decisions they do throughout the teaching process. Furthermore, because inservice and preservice teachers differ in experience and available resources that they draw on while making decisions, it is helpful to consider the resources PSTs' draw on while reasoning. Curricular reasoning is a framework that describes teachers' thinking processes when making decisions during the teaching process. This study investigated secondary preservice teachers' decisions and curricular reasoning throughout the teaching process. Data were collected from two groups of secondary preservice teachers in a mathematics methods course focused on student thinking and mathematics. Results revealed that the preservice teachers used all seven curricular reasoning strands, especially drawing on mathematical meanings, mapping learning trajectories, and considering learners' perspectives. Specifically, this study demonstrates ways in which preservice teachers reason about their decisions and the intertwined nature of their curricular reasoning. The results from this study also imply that it may be helpful to consider the resources PSTs have access to, including their instructor, and that the order of their lesson planning may allow support for the mathematical learning trajectories within individual lessons. This study also provides validation for the curricular reasoning framework described by Dingman, Teuscher, Olson, and Kasmer (in press), provides subcategories of curricular reasoning strands, and has implications for teacher education.