Assessing the achievement of students in elementary and secondary schools and the nation's educational progress is fundamental to informing education policy approaches. Congressional interest in this area includes and extends beyond the annual assessments administered by states to comply with the educational accountability requirements of Title I-A of the Elementary and Secondary Education Act (ESEA). Congressional interest in testing also encompasses a national assessment program, authorized by the National Assessment of Educational Progress Assessment Act (NAEPAA; Title III, Section 303 of P.L. 107-279), and participation in international assessment programs, authorized by the Education Sciences Reform Act (ESRA; P.L. 107-279, Section 153(a)(6)). At the national level, students participate in the National Assessment of Educational Progress (NAEP). At the international level, U.S. students participate in the Trends in International Mathematics and Science Study (TIMSS), Progress in International Reading Literacy Study (PIRLS), and Program for International Student Assessment (PISA). When national and international assessment results are released, there is a tendency to take the results of one assessment and present them as a snapshot of U.S. student achievement. The focus on one set of assessment outcomes may result in a narrow and possibly misleading view of overall student achievement. The primary purpose of this report is to provide background and context for the interpretation of national and international assessment scores so that results can be interpreted appropriately over time and across multiple assessments. Other purposes of this report are to describe specific national and international assessments, describe the recent results of these assessments, and clarify specific issues regarding the interpretation of assessment scores that explain the achievement of U.S. students.