Almost every time the results of an international test of student achievement are released to the world, the reaction among the American public and policymakers is like that of a parent whose child just brought home a disappointing report card. Elected officials and academic experts question where U.S. students fell short: Was it their curriculum, their teaching, or a confluence of out-of-school factors? What did other nations do well? And what changes to American classrooms would help U.S. students make strides on the next round of tests? Despite such reaction, many observers--even those who interpret the test scores very differently--say that American policymakers need to guard against simplistic interpretations of the results of PISA, TIMSS, or PIRLS, the acronyms for three high-profile tests given periodically to samples of students in dozens of countries. Similarly, researchers and test experts urge U.S. officials to be cautious in the lessons they draw from the impressive scores of high-performing Asian and European nations.