In this dissertation, I present my research on STEM foundational thinking and instructional activities at the elementary-school level. Specifically, (a) What elementary school structures support students in STEM curricular areas? (b) Do these supports differ for students of color? (c) What are the components of elementary STEM opportunities to learn that foster interest, participation, and academic success in STEM foundational thinking, especially for marginalized students? I discuss our modified activity theory framework (CHAT). Systemic racism contributes to the diminished capacity of children of color in STEM curricular courses. There is a lack of diversity not only in STEM education classes, but in the STEM career pipeline. Our research team analyzed schools as effective learning organizations. My specific focus was on STEM equity and access to STEM foundational thinking. Specifically, I researched access to STEM curricular activities in the elementary grades (K5) because research shows that it is in these early years, students of color find their natural interest in STEM supported or discouraged through access (Wiebe et al., 2013). Chapter one introduces the problem of STEM inequity in public education, describing the purpose and significance of this research, definition of terms, and my assumptions, limitations, and delimitations. Chapter two reviews the current literature on race, equity, and STEM-foundational thinking and leadership practices, emphasizing the importance of applying a Critical Race theoretical framework and culturally responsive pedagogy in order to highlight inequitable access to STEM curricula for students of color as well as the hegemony currently present in many STEM programming. Chapter three focuses on the mixed methodology used for this research, including the research design, data collection and analysis procedures. I present my research findings as organized by my STEM research questions. Finally, I conclude in chapter five by discussing the findings as well as my suggestions for future research and pedagogical practice. It is my hope that this research will guide others in creating significant, positive gains for students who have been marginalized due to the color of their skin.