Implicit in the frame of reference hypothesis is the assumption that s
ocial comparison is one of the causal determinants of self-concept. Th
e present study of Norwegian sixth-grade elementary school students sh
owed that students of low-, medium-, and high-achievement classes did
not differ in mathematics self-concept. Mathematics self-concept was,
however, significantly influenced by the students' within-classroom po
sition in mathematics. The results support the frame of reference hypo
thesis, and the support was consistent over gender.