This article presents research findings from a professional development project initiated by one rural Illinois primary school to improve writing instruction in 2nd and 3rd grade classrooms. During the 2010–11 academic year, the school partnered with a private university to provide customized, year-long professional development that integrated preparation for the state writing assessment and a writing process approach. Simultaneously, a study was conducted to identify and describe teacher thinking and practices related to writing instruction during participation in the project. Data were collected through a pre/post teacher survey and written teacher reflections. Participating teachers indicated 15 improvements in their thinking and practices related to writing instruction. However, confidence in their students’ likelihood to perform well on the state writing assessment decreased during the project, and changes in thinking and practices varied from teacher to teacher, possibly due to varying levels of teacher readiness to change.