This study examined the impact of sense of belonging on student engagement in math and science classrooms at an all-girls middle school. The sample was comprised of 129 seventh and eighth-grade students in three math classrooms and three science classrooms in an independent, urban all-girls middle and high school. My research design applied explanatory mixed methods, beginning with a survey, and ending with a focus group, in order to identify what factors students identified to contribute to their sense of belonging, and if these factors impacted their engagement in math or science class. Once survey data were collected, I analyzed the correlations to identify specific sense of belonging factors with strong, positive correlations to specific engagement questions. Next, I coded data from the focus group, identifying areas when students expressed feeling a sense of belonging or actively engaging in math or science class. Then, I compared data from the survey and the focus group to identify commonalities between sense of belonging factors appearing in the classroom and how they impacted a student's engagement. My findings support the extant literature on sense of belonging; moreover, the findings specifically identify factors like agency, encouragement, and understanding. These specific factors may allow educators with specific targets to employ interventions, should a student's engagement decrease. Essentially, an educator can target a sense of belonging factor, apply the appropriate intervention, and see a positive shift in the student's engagement in class. Ultimately, this study highlighted specific strategies for educators to bolster a student's sense of belonging in math or science class at an all-girls middle school. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]