Over the past 25 years, achievement goal theory has emerged as one of the most prominent theories of achievement motivation. This chapter uses an achievement goal framework to examine the influence of classroom and school environments on students' academic motivation and achievement. Considerable evidence suggests that elementary and secondary students show the most positive motivation and learning patterns when their school settings emphasize mastery, understanding, and improving skills and knowledge. Whereas school environments that are focused on demonstrating high ability and competing for grades can increase the academic performance of some students, research suggests that many young people experience diminished motivation under these conditions. The implications of achievement goal theory for examining the impact of school reform are discussed.