The authors investigated the relationship between self-perceptions of ability and achievement in math, science, and English from Grades 8 to 11 (N = 342). A state-trait model that included an association between stable (i.e., trait-like) components of self-perceptions and achievement as well as time-specific (i.e., state-like) effects during the transition to high school (i.e., Grade 8 to Grade 9) demonstrated superior fit to alternative models that did not incorporate these features. Stable components of self-perceptions of ability and achievement exhibited a substantial association in this model. In most instances, however, there also was evidence of a positive effect of self-perceptions in Grade 8 on achievement in Grade 9.