This synthesis project would collect empirical studies of teacher professional development in mathematics or science and conduct a meta-analysis of them. The studies would be located from recent evaluations of MSP project, state agencies, and various other places that are yet to be announced by the researchers and are expected to be more abundant because of the demands of federal programs and NSF funding for the MSP. The purpose of the study is to measure the extent to which improving teacher quality, through improved preparation, is effective. The statistical measurements would include student achievement as well as teacher development measures. The study would provide information across states as well as national averages about the extent to which teacher understanding of content areas makes them more effective teachers.