Stage-environment fit theory posits that the interpersonal dynamics and structural (i.e. school-level) resources afforded by a student's academic environment can either support or thwart student thriving (e.g. achievement). Thus, it is important to examine how these factors impact student achievement at the student- and school-level. This investigation utilized the 2015 PISA data set (N = 210,381 students in 7964 schools from 32 OECD countries) to examine the extent to which school belonging (supporting) and teacher unfairness (thwarting) predict students' achievement (in reading, mathematics, and science) at both the student- and school-level. Findings indicate that at the student-level (but not school-level), teacher unfairness significantly thwarts achievement; in contrast, at the school-level (but not the student-level), school-belonging significantly supports achievement. These findings suggest that distinct interpersonal dynamics differentially impact achievement more saliently either at the student- or school-level -- underscoring the importance of conducting multilevel modelling when investigating these social phenomena.