The purpose of this study was to explore the development of students' understanding through writing while immersed in an environment where there was a strong emphasis on a language-based argument inquiry approach. Additionally, this study explored students' spoken discourse to gain a better understanding of what role(s) talking plays in the development of understanding through writing. Finally, the study proposed a new concept of Discourse Space, which enabled researchers to improve their understanding of the characteristics of the development of student cognition through writing, and of the roles talking plays in cognitive development through writing. This study was guided by the research question: What patterns of the development of fifth grade students' cognition over time emerge in their private and public negotiations under a teacher who is ranked as a low-level implementer of the SWH approach? This question was divided into two sub-questions: (a) Throughout a unit, Ecosystems, what patterns emerge regarding the development of six fifth grade students' understanding through writing, and b) What patterns of the development of Discourse Space emerge through talking in three different contexts. In order to answer these questions, this qualitative research employed a generic qualitative study. Twenty-one fifth grade students participated in this study, and six students were purposefully selected through which to further investigate the development of an understanding of science through private negotiation while immersed in a language-based argument inquiry approach. Major data sources included students' writing samples, informal conversations with the teacher, researcher's field notes, and classroom videos. Additionally, the teacher's modified RTOP scores and semi-structured interviews were used to deepen the contextual understanding of the learning environment and the teacher's instructional performance. The data analysis was conducted by utilizing discourse analysis of writing and talking. The results showed (1) students' low level of engagement in evaluation impacted their reasoning and use of sources for making meanings, as well as their understanding of the topic. Compared to the results of a previous study, students' complexity of reasoning was relatively less developed, and similarly students' use of reflective sources was generally observed relatively less often. (2) The teacher and students in this study engaged in limited public negotiation, which focused more on articulating than on evaluating ideas. The limited public negotiation that was represented by the dialogical patterns in this study cannot support the development of understanding through writing or the practice of the roles of constructor and critiquer, which play a core function in the comprehension of scientific practice. This study has several implications for teacher education and research. Teacher education needs to be centered more on how to encourage students' engagement in the process of evaluation, since this plays an important function not only in the development of understanding, but also in providing opportunities to perform the roles of both constructor and critiquer. Teachers can use writing as an argumentative activity to encourage or foster students' engagement in the process of evaluation or critique. Additionally, this study provides insight into the importance of the learning environment in which the teacher and students create and develop; this learning environment needs to provide not only opportunities but also demands for students to engage in both constructing and critiquing ideas. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]