A contextual approach to understanding class size reduction includes attention to both educational inputs and processes. Based on our study of a class size reduction program in Wisconsin we explore the following question: How do class size reduction and classroom quality interact to produce learning opportunities in early elementary classrooms? To address this question, we analyze data from 3 years of fieldwork in 27 classrooms in 9 schools implementing a class size reduction reform. Data generation included multiple ethnographic observations and interviews with teachers and principals, administration of the Classroom Assessment Scoring System, document and artifact collection, and analyses of school-level standardized test scores. We present multiple vignettes to illustrate that class size reduction provides opportunities that can be activated by organizing and implementing high-quality classroom practices. We argue that high-quality classrooms combined with class size reduction contexts create a synergy for learning. (Contains 7 notes, 3 tables, and 4 figures.)