Does Teacher Professional Development Affect Content and Pedagogical Knowledge: How Much and for How Long?

We examine the impact of teacher professional development on knowledge growth and subsequent knowledge retention. Specifically we use English Language Arts teacher content and pedagogy assessments to determine whether the California Professional Development Institutes significantly improve teacher content knowledge and whether teachers retain that knowledge six months after the institutes are completed. The results indicate that teachers vary significantly in pre-institute knowledge on the four assessed domains, demonstrate significant knowledge growth, but only retain about one half of what was gained during the institute. Further, pre-existing knowledge gaps are not systematically reduced and teacher perceptions of institute quality are not related to knowledge growth and knowledge retention.