Causal Mediation Mechanisms in Inquiry-based Science Professional Development.

摘要

This study contributes to better understand the key mediation mechanisms involved in the relationship among teachers' professional development, reformed practices, and student outcomes. In an attempt to unpack the causal mechanisms of professional development, this dissertation raises two main questions: 1) How do reformed classroom practices mediate the relationship between professional development and student outcomes? and 2) How do different levels of school organizational capacity, including professional community, principal support, and teacher buy-in, moderate the effects of professional development? To examine the research questions, this dissertation uses data from the Los Angeles Unified School District (LAUSD). The intervention was randomly assigned to 80 schools, including 40 treatment and 40 control schools. In light of the research questions, the analytical strategies are threefold. First, this study decomposes the effect of an inquiry-based science professional development into the direct and indirect effects using causal mediation effect analysis. Second, although teachers intend to implement key principles of effective professional development, specific implementation gaps undermined and contradicted these efforts. Therefore, this study defines the implementation gap between what this professional development intended to change and what actually has been accomplished. Given the different measures of implementation, this study examines which schools and teacher characteristics contribute more to the changed instruction. The third analysis examines why the professional development yields negative student outcomes in the treatment schools. The findings of this study show that inquiry-based instruction does not significantly mediate the effect of professional development on student outcomes. The results indicate that the mediation effect of inquiry-based instruction between professional development and student outcomes is positive but not significantly different in the control versus the treatment. However, the direct effect of the professional development on student outcomes is negative and significant. The negative direct effect may emphasize the importance of school environment when implementing new programs, including factors such as how capably teachers and principals manage new programs. Regarding the measures of implementation outcomes, this study focuses on the implementation gap and school organizational capacity that may influence the gap. The findings suggest that teachers benefit from the treatment by increasing the number of any inquiry features in their instruction when they perceive that their principals are supportive. This finding indicates that school leadership plays an important role for teachers in implementing new teaching approaches. With respect to the relationship between inquiry-based instruction and students' science performance in the treatment schools, the results suggest that students taught by teachers with fewer than 3 years of teaching experience obtain lower scores than students taught by more experienced teachers. However, students of novice teachers benefit more from the use of inquiry-based instruction than students of more experienced teachers. The results underscore that implementing new instructional practices is multilayered with school resources and organizational capacity. To reduce the implementation deficit, cohesive support from school organizations and leadership is vital. Therefore, this study provides insights into how professional development influences student outcomes as mediated by teachers' transformed instruction, and also why this effort has yielded unexpected outcomes.