Achievement emotions, defined as the emotions generated in the academic process or by achievement results, are critical for an individual’s mental health, personality development, and academic productivity. Referring to the well-known big-fish-little-pond effect on academic self-concept, which describes the well-known phenomenon that students in selective schools/classes tend to have lower academic self-concepts than those who are comparably competent but attend regular schools/classes, Pekrun and colleagues focused on German students and proposed a similar happy-fish-little-pond effect on achievement emotions in 2019. In our paper, we examined whether this effect exists in extreme cases. To maximize the positive reflected-glory effect of being in a selective school and minimize the negative social comparison contrast effects that result from being ranked low in the school, we conducted an investigation in the Chinese collectivist cultural setting and compared the achievement emotions of students from a highly selective senior middle school with those of students from a regular school where the top-ranking students fell short of the bottom-ranking students in the selective school in terms of academic performance. Through an analysis of variance and a moderated serial mediation model, our study revealed that the bottom-ranking students in the selective school had less positive achievement emotions, lower academic self-concepts, and more negative achievement emotions than the top-ranking students in the regular school, providing strong evidence that students rely more on social comparison than on objective self-evaluation standards to evaluate themselves. The implications of the results for educational policies are discussed.