The purpose of this study is to investigate whether teacher support mediates the relationship between students' sense of school belonging and academic achievement. Using 2 case periods of panel data from the Connecticut Department of Education, I used Baron and Kenny mediation analyses and a fixed-effects regression model to investigate data from a subset of 9th graders who participated in the survey in 2014. The same group of students participated in the same survey in 11th grade in 2016. There were 30,580 participants with both 9th- and 11th-grade data. This study finds that student perceptions of teacher support significantly explain the relationship between school belonging and academic achievement while controlling for school absences, socioeconomic status, school suspensions, minority status, and credits earned. These findings contribute to the existing literature on factors that explain variations in student achievement by teasing out the independent influence of school belonging vis-a-vis teacher support. [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.]