While there is extensive research related to the study of high-quality professional development, the research shows that there is limited evidence to indicate that teachers are provided with this type of professional development on a consistent, ongoing basis. The research also suggests that there is a lack of adequate evidence to show that professional development is being successfully targeted to those teachers who need it (Porter, Garet, Desimone, Yoon, & Birman, 2000; Sykes, 1996). This dissertation constitutes a case study of one professional development model, teacher study groups, commonly called a "differentiated" model, namely one that is aimed to help specific teachers with distinct help. The differentiated model that this study examined is modeled after the teacher study group (TSG) concept. This study used survey and interview methods to collect data about the history of the model used during this study, the practice itself, the participants in the specific case, the participants' perceptions of their experience, and the process and outcomes, as well as other related features. A survey was distributed to all 22 regular, K-6 classroom teachers employed at one elementary (K-6) school that served as the subject in this study. Interviews were also conducted with the professional development provider, the site principal, and 4 classroom teachers. Results of the study were compared with previous work on the subject and suggestions for further research were made. In particular, implications for practice were offered with regard to the TSG model for use as a differentiated professional development program. [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/en-US/products/dissertations/individuals.shtml.]