Taking the well-documented high educational expectations among immigrant parents as a point of departure, we explore how average achievement in a class influences parental educational expectations. Specifically, we investigate whether reference group (i.e., big-fish-little-pond) effects can account for immigrant parents' higher educational expectations for their children compared to nonimmigrant parents. We address this question by applying a multilevel (mediation) analysis to a representative sample of German fourth graders and their parents. To test how robust our findings are to our data-analytical decisions, we additionally conduct a multiverse analysis. We find consistent evidence across 4,608 model specifications that parents' educational expectations are higher when their child attends a low-achieving class compared to a high-achieving class, even after controlling for students' individual school performance, socioeconomic background, and a variety of performance related confounders. Furthermore, (average) class achievement partially mediates the relationship between immigrant status and parental expectations. Students with immigrant parents are more likely to attend low-achieving classes, which is positively related to higher parental expectations. Our results suggest that big-fish-little-pond effects also operate in parents' evaluation processes of their children's educational attainment.