This study tested whether students' motivation and perceptions of the learning environment changed significantly within the school year. Korean high school girls' (N = 375) perceptions of the performance goal structures in the environment increased significantly throughout the school year. The girls' personal achievement goals and task value demonstrated few significant within-grade changes, but their self-efficacy fluctuated significantly around examinations. Motivational beliefs were more stable than were perceptions of the environment. Nevertheless, the modified perceptions of the learning environment explained changes in motivation, justifying continued efforts to create a motivationally adaptive environment. Construct relations were consistent across different academic contexts. There was no evidence that low-achieving girls responded more negatively to the classroom performance goals than did their better-achieving peers.