Although an increasing number of research studies in mathematics education have begun focusing their efforts on mathematical modeling as a need for change to convey mathematical ideas beyond schools, there is not enough information about the nature of the teacher knowledge for effective use of modeling in mathematics teaching and how this knowledge evolves. The goal of this study is to investigate teachers&rsquo / evolving knowledge when they engage in professional development activities based on lesson study cycle from modeling perspective. Professional development program of this study included a cyclical process. Lasting a month, each cycle consisted of meeting before the implementation of the model eliciting activity, implementation of the activity and meeting after the implementation. The study took five months and was conducted in two public schools. The participants were four in-service mathematics teachers where two teachers were selected from each school by purposive sampling. The study was designed as case study. Data analyses were conducted during and after data collection and with two approaches as with-in case and cross-case analysis. As the professional development activities created learning environments for the teachers to develop their models for teaching mathematics from a modeling perspective, the results of this study showed that the professional development program used in the study had a positive effect on teachers&rsquo / evolving pedagogical content knowledge and pedagogical knowledge based on the theoretical and empirical backgrounds in the literature. Besides, implications, suggestions for professional development, for teachers and for further research are provided.

The NYC Teaching Fellows (NYCTF) program, as the nation’s largest alternative certification program, aims to provide high-needs NYC public schools with highly qualified teachers in such hard-to-staff areas as math, science, and special education. Reports of NYCTF teacher retention are mixed; The New Teacher Project (TNTP) claims high retention rates, but other research indicates that fellow recruits have lower retention rates than other teachers in similar NYC schools – only Teach for America (TFA) exhibits higher attrition (Boyd et al., 2006). After scrutinizing these contrary claims, this paper examines the retention of a recent cohort of approximately 300 Mathematics Teaching Fellows (MTFs) in the NYCTF program, examining MTF’s early attrition, movements from school to school in the NYC system, and professional plans for the future. We also include findings on teacher induction, school leadership, and school context that affect MTF retention.