Over the past 3 years, teacher union membership has significantly decreased in the state of Georgia. This decrease in union membership is troubling, as previous research has shown that union membership is positively connected to teacher satisfaction and, in turn, to student success. The purpose of this qualitative case study was to determine why members were leaving, and why other teachers remained in the union. Senge's systems theory served as the conceptual framework for the study. Data collection included personal interviews with 5 current union members and 5 former union members, where they were asked if they had received the union services they expected in terms of legal representation, advocacy, and professional development. Line-by-line coding, axial coding, and theoretical coding procedures were used to identify emerging categories. The emerging themes were (a) availability of liability insurance, (b) representation and sense of security, (c) advocacy, and (d) communication. These findings display both current and former members' need for a strong union presence within the daily school environment, as well as their professional state of affairs. This study has the potential to support positive social change as it will educate union leaders on the needs of their members. Potentially, new and current members will reap more satisfaction from the union, which may lead to more effective teaching and increased student achievement. [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.]