Previous research has provided mixed results regarding the effect of anxiety on academic achievement. Building on this body of research, the present longitudinal study pursued two goals. The first goal was to describe trajectories of anxiety during elementary-school years. The second goal was to determine the predictive value of these trajectories on high school noncompletion after controlling for personal (i.e., gender, classroom behaviors, and academic achievement) and familial (i.e., sociofamilial adversity) characteristics. A community sample of 1,817 children (887 boys, 930 girls) participated in this study. Results showed that anxiety tended to fluctuate from kindergarten to Grade 6 for different groups of children. Furthermore, the result of a logistic regression analysis indicated that group membership for anxiety predicted high school noncompletion by age 20. As a whole, these findings suggest that considering heterogeneous developmental patterns of anxiety during elementary-school years appears quite useful for predicting an important outcome such as high school noncompletion.