Compared to the vast literature on the cross-sectional relationships between cognitive and noncognitive factors and academic performance across all stages of schooling, relatively few studies have explored these relationships longitudinally at the high school level, especially in students who exhibit high academic performance. In this study, surveys of self-efficacy, locus of control, and intrinsic motivation were administered to 8,586 applicants to a prestigious private college-preparatory high school during the admissions process; simultaneously, standardized test scores (SSAT) were obtained. Enrolled and nonenrolled students were compared on prior academic performance and noncognitive measures. Further, noncognitive variables and trajectories of GPA (grade point averages) across 4 years (12 time points) were explored among the enrolled students (n = 818). The enrolled students, compared to the nonenrolled, showed advantageous scores on all measures. Also the relationships between noncognitive measures and academic performance were more weak between the enrolled than the nonenrolled students. Finally, a latent class growth analysis showed four trajectories of academic performance among the enrolled students. The only noncognitive measure distinguishing the students in different trajectories was anxiety about their own self-efficacy. The differences in the relationships between noncognitive measures and academic performance in high-achieving students in a high performance environment will be discussed.