The purpose of this study was to develop an understanding of the effect of a single-gender intervention on the STEM Education Outcomes and STEM Identity Outcomes of females in STEM, as well as an understanding of the experiences of the female participants of the single-gender classroom. The conceptual framework was based on Maslow's Hierarchy of Needs Theory and Csikszentmihalyi's Flow Theory to provide the structure for support of female student interest in STEM education and careers through fostering success, measured through STEM education outcomes and STEM identity outcomes. A transformative, parallel mixed methods approach was used for this study to allow for the collection and analysis of quantitative and qualitative data with the intent of integrating the results to better answer the research questions. In this study, 28 female students experienced the first course in the PLTW engineering pathway in a single-gender classroom setting, rather than a traditional setting. Students were monitored not only through the semester, but through high school graduation. Students were compared based on the final course grade, PLTW end of course assessment, number of additional STEM electives taken, and the number of STEM extracurricular activities. Students in the single-gender intervention group also completed a survey at the end of the course, and 7 students completed a survey after leaving high school. The single-gender intervention significantly impacted students' scores on the PLTW end of course assessment, indicating an increase in knowledge retained over the semester. There was also a significant increase in the number of additional STEM electives taken by students in the single-gender intervention group. Analysis of the data showed that there was no significant increase in the final course grade or the number of STEM extracurricular activities because of the intervention. The findings of this study support the implementation of interventions such as the single-gender classroom because they can promote the development of STEM identity, leading more women to choose STEM career paths. [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.]