<p>Changes in performance over time can provide important information about one’s ability and effort. Three preregistered studies examined how children aged 4 to 10 perceive and evaluate academic performance changes (<i>N</i> = 256; 131 girls, all Han ethnicity, China). When evaluating two characters with matched final performance but different performance trajectories, with age, children increasingly perceive the character with improving performance as less smart but more hardworking than the one with constant performance, and they evaluate the improving character more favorably than the constant character (Studies 1 and 2). However, they increasingly favor a constant character over one with declining performance (Study 2). When the improving character outperforms the constant character in the final performance and overall performance is matched (Study 3), even 4- to 6-year-olds favor the improving character over the constant character. These findings highlight children’s developing ability to flexibly reason about and evaluate changes in performance over time.</p>