Trends and exemplary practices of STEM teacher professional development programs in K-12 contexts: A systematic review of empirical studies

STEM teachers are critical mediators of knowledge, and their performance can directly impact students & rsquo; learning experiences and knowledge acquisition. To ensure the quality of STEM in-struction, countries worldwide have launched STEM teacher professional development (TPD) programs. It is paramount to know how these programs have been implemented and what lessons can be learned from them. In this study, to capture the trends in publications on K-12 STEM TPD, we systematically reviewed relevant journal papers published in the Web of Science database from 2006 to 2020. We analyzed the (1) knowledge foci, (2) professional development ap-proaches, (3) outcome measurements, as well as (4) data sources of the STEM TPDs. In addition, to inform future professional development designs, we selected and developed narrative de-scriptions of three exemplary cases. These cases showcased high-quality TPD and covered pre -service and in-service teachers in formal and informal settings. We reviewed the knowledge foci of the STEM TPDs using the technological pedagogical content knowledge (TPACK) frame-work. The results showed that the types of knowledge delivered in the STEM TPD programs were mostly pedagogical knowledge and pedagogical content knowledge, while a certain number of programs focused on technological content knowledge and technological pedagogical content knowledge. Most of the studies adopted mixed professional development approaches, featuring activities like learning by design, learning by doing, reflective learning, and group work. These approaches emphasized the active participation of teachers in the process, built links between content and classroom practices, and encouraged collective participation in developing expertise. However, the data were mostly collected through interviews or survey instruments. Future research should move beyond analyzing data on teachers' perceptions to explore processes (e.g., online participation logs, teacher-peer interactions) and products of performance (e.g., lesson plans, handmade crafts) to further examine the effects of STEM TPD activities. It would also be desirable to establish greater consistency in data collection approaches, such as by using validated interview or observation protocols that are generalizable to different school settings.