Teacher attrition is problematic in schools serving marginalized populations. Teacher attrition rates are 50% higher in Title I schools than in non-Title I schools (Carver-Thomas & Darling-Hammond, 2017). Furthermore, attrition among teachers whose main teaching assignments are in mathematics and science is 70% higher in Title I schools as compared to mathematics and science teachers in non-Title I schools. This study investigates mathematics and science teachers who enter the profession through Teach for America (TFA), which places thousands of teachers in high-needs schools for a two-year commitment. While existing research on TFA literature has investigated the final decisions made by TFA teachers regarding their post-commitment plans, the process by which the teachers develop their post-commitment plans throughout their first two years in teaching, and the extent to which their plans change throughout these years is unknown, as is the role of TFA teachers' support networks in this decision-making process. Focusing on the Massachusetts cohort that began teaching in the 2018-2019 school year, this study explores how ten TFA teachers developed, maintained, and used support networks using three semi-structured interviews with the teachers during their second year as teachers. I also develop a model for the teachers' decision-making processes regarding their intended plans and the role of the teachers' support networks in these processes. Finally, implications of this deepened understanding of the teachers' decision-making process on teacher education programs, TFA, the schools/districts where the teachers are placed, and on future research on teacher retention are explored. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]