The Progress in International Reading Literacy Study (PIRLS) is an assessment of the reading comprehension of students in their fourth year of schooling. In 2006, PIRLS was administered to a nationally representative sample of fourth-grade students in the United States, as well as to students in 44 other jurisdictions around the world. The PIRLS assessment measures student performance on a combined reading literacy scale and on a literary subscale and informational subscale. This book compares the performance of U.S. students with their peers around the world and also examines how the reading literacy of U.S. fourth-grade students has changed since the first administration of PIRLS in 2001. Results are presented by student background characteristics (sex and race/ethnicity) and by contextual factors that may be associated with reading proficiency (school characteristics, instructional practices and teacher preparation, and the home environment for reading).