Professional development (PD) is a potentially important mechanism for enhancing classroom practices and children's learning. In this large-scale randomized controlled trial, we examined the effectiveness of language and literacy PD, with and without coaching, offered at scale to early childhood educators (n ϭ 546) across 1 state. Relative to the comparison condition, PD with coaching showed a small impact on the quantity of phonological awareness instruction, and PD with and without coaching impacted the quality of phonological awareness and writing instruction. PD did not impact children's (n ϭ 1,953, M age ϭ 4.53) emergent literacy skills, as measured by the research team, or kindergarten readiness, as measured by the state's kindergarten readiness assessment which exclusively focused on language and literacy skills. Although we can only speculate as to why this at-scale, state-sponsored PD did not realize intended impacts, these findings, as coupled with those from the literature, raise critical questions concerning current understandings of PD and the ability to achieve desired effects when implemented at scale.
Educational Impact and Implications StatementIn the field of education, professional development is intended to improve classroom instruction and children's learning. However, we have a limited understanding as to its effects, especially when used at scale with large numbers of educators. In this study, we examined the language and literacy professional development offered to early childhood educators by one state. We found that the professional development affected only a few aspects of classroom literacy instruction and did not affect young children's literacy learning. These results suggest that, in order to be effective, at-scale professional development may require greater attention to design and implementation and highlight the need for pilot work regarding effects of professional development prior to large-scale investments.