This article examines the reading of leveled books and the assessment of students' reading levels in a public school classroom. The purpose of the research study was to examine how these processes of assessment, which often go unnoticed, shaped the ways reading and readers were defined. The research was located in a third grade, public school classroom in a large metropolitan city in the United States. Theoretically grounded in sociocultural perspectives on literacy and poststructural notions of power and positioning, the research methodology involved a series of nested case studies of the classroom as a whole and of one particular reader, whose performances allowed a more nuanced understanding of the dynamics of reading levels and reading leveled books in the particular classroom. Data analysis involved the thematic analysis of reading events with the purpose of identifying the materials, norms, and routines connected to reading leveled books. Attention was paid to processes of naming, to students' efforts to discipline selves and others, and to the meaning of reading as measurable that extended beyond the boundaries of the local classroom and into broader institutional contexts. This allowed tracing and interpreting the productive and regulatory power of leveling. The findings show that reading leveled books and assessing students' levels were integral parts of schooled literacy as performed in the particular classroom. The study offers grounded theoretical hypotheses about the intersection of reading instruction and assessment and calls readers to consider the complexities of reading and reading instruction in elementary classrooms. (Contains 1 note.)