Teacher professional development is essential to education reform. In this study, professional development was viewed as a method for increasing teachers' social capital - the resources that they can access through peer collaboration to support their ongoing learning. This study compared the social capital generated during two different types of collaborative meetings. During highly-structured meetings, teachers shared their own personal practical knowledge and offered each other advice and assistance. During loosely-structured meetings teachers worked together to improve their lessons using a new model for effective instruction. The research approach adopted for this study led to the new concept of "learning community closure" as one possible way in which professional development could increase teachers' access to social capital. This study also introduces a "taxonomy of teacher social capital" which could be used to help researchers describe the effects of professional development activities. [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.]