The purpose of this project was to examine the effectiveness of the Targeted Reading Intervention (TRI) professional development program in helping rural kindergarten and first-grade classroom teachers in low-wealth schools implement evidence-based, individualized reading instruction for the children in their classrooms who are struggling in learning how to read. Specifically, it aimed at understanding whether the TRI can improve teacher knowledge in both the foundation and the pedagogy of the teaching of reading, but, more importantly, understanding whether the TRI can improve teacher practices in the teaching of reading that are linked to reading gains for struggling readers. The TRI was initially developed and tested via a series of small, randomized clinical trials. Results yielded large effect sizes for student outcomes (.4 to .7) that highlight the need to validate the mechanisms of change for teacher pedagogical content knowledge and practice through a large randomized controlled field trial.