Modern societies rely on written tests. Achievement tests have come to play a prominent role. They are used to sift and sort people, to evaluate schools, and to assess the performance of entire nations. This book evaluates the predictive power of achievement tests for life outcomes by examining one widely used achievement test --- the General Educational Development test --- the GED for short. The GED enables high school dropouts to certify high school equivalency. Currently the GED program produces roughly 12% of all high school credentials issued in the U.S. GED recipients are as smart as high school graduates who do not attend college. On outcomes that matter, as a group GED recipients are not equivalent to high school graduates. High school graduates outperform GED recipients in terms of their earnings, employment, wages, labor market participation, alcohol use, self-reported health, crime, college completion, welfare receipt, and other meaningful outcomes. This study of the GED program gives strong evidence on achievement tests. They do not adequately capture character--personality skills like conscientiousness, perseverance, sociability, and curiosity, that are valued in the labor market, in school, and in many other domains. Differences in character skills emerge early between GEDs and high school graduates and are related to conditions in early family life. Both cognition and character can be shaped, and change over the life cycle. These skills can be enhanced by intervention.