This brief presents results from a study that examined levels and patterns of change in classroom quality over a school year, and the way those changes vary by different quality dimensions. The study is based on data from the Expanding Children’s Early Learning (ExCEL) Quality project, which assessed two different approaches to improving classroom quality. The findings suggest that practitioners and policymakers should carefully consider the timing and number of quality ratings when making decisions about how to improve programs and monitor processes. This brief examines how biweekly ratings by teachers’ coaches of three dimensions of classroom quality-structural, interactional, and instructional quality-changed over the course of the study (which occurred from September 2019 through March 2020). It addresses two research questions: How do different dimensions of quality change over time? How do changes in the three dimensions of quality differ based on the curricular and professional development approach? (author abstract)