Background: A growing literature focuses on reasons behind achievement goal endorsement, and mastery-approach goals (MG) specifically, and how these reasons influence academic performance. Past research provides evidence that student-level social value-related reasons behind MG moderate the MG-performance link in adolescents and young adults. However, we ignore whether this moderation is best conceived of as a student-level effect (i.e., students' social value-related reasons), a class-level effect (i.e., influence of class-dependent contextual social value), or both. Aims: This research aims at understanding the moderation of the MG-performance link by social value from a multilevel account, which is novel, as the student level has been the default level so far. Sample: The study was conducted on a sample of 436 primary school students, from 3rd to 6th grade. Methods: Students completed a MG scale adapted to their French classes under different instructions: standard, social desirability (answer to be viewed as likeable by your teacher), social utility (answer to be viewed as successful by your teacher), along with a dictation to measure performance, and socio-demographic measures. Results: Results show that the moderation effect of social utility on the MG-dictation performance link is observed at the student level, but that the moderation by social desirability is best accounted for by class-level differences. Conclusions: It is important to consider a multilevel framework when examining reasons behind MG reports, including social value-related reasons, both for future research and teachers in the classroom.