This study was set to investigate how a cohort of ten Indonesian teachers experienced transformations in their teaching professionalism upon receiving an assignment of instructional leadership training to other school leaders. These ten teachers, who came from three different Indonesian Jesuit high schools and one archdiocese-based educational foundation in Jakarta, belonged to an initiative called Indonesia Secondary Education Development Program (ISEDP) intended to develop instructional leadership skills among school administrators in Indonesia. This six-year initiative (2006-2012) involved three international institutions, namely Loyola University Chicago (LUC), Indonesian Jesuit High Schools Association (IJSA), and Sanata Dharma University (SDU), Indonesia. The goal was operationalized into two major programs. The first was to prepare a cohort consisting 12 participants: 11 men--including two Jesuit priests--and one woman. In this preparatory phase, the twelve participants attended a specifically designed masters degree program in Instructional Leadership using a training-for-trainers framework at Loyola University Chicago. Second, upon the completion of their study at Loyola University in Summer 2009, the 10 cohort members returned to Indonesia, while two of them remained in Chicago to continue their doctoral studies at Loyola University Chicago. This study was set to capture the transformative learning undergone by these ten teachers as they retrospectively reported in the first four years of their collaboration in the cohort group. It was assumed that the dynamics taking place in the cohort group, the learning materials they studied together in the same classes, and exposure to different socio-cultural schooling experiences would provide them with opportunities to acquire knowledge, skills, and develop appropriate attitudes to help other school leaders in their home country. This study utilized phenomenological methodology in order to capture personal transformations of each cohort group member. This study found that all participants acquired a variety of knowledge related to instructional leadership, developed necessary skills to deal with the instructional leadership training program, and developed appropriate attitudes which made them more adaptive and resilient in the face of dire circumstances. This study, however, found that each participant demonstrated different levels of transformations. Two conclusions were drawn from this study. First, cohort group model as a learning design for adults played an important role in providing contexts for professional growth among these ten teachers. Second, the phenomenological investigations was useful to capture the transformative learning of the participants. [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.]