In the present study, we tested the hypotheses that: a) there are individual differences in secondary students' conceptual and procedural fraction knowledge, and b) these differences are predicted by students' approach (deep vs. surface) to mathematics learning. We used two instruments developed and evaluated for the purposes of the study which were administered to 463 students at seventh and ninth grade. We found four clusters of students corresponding to different ways of combining conceptual and procedural knowledge of fractions. Students' approach to mathematics learning predicted membership to some, but not all clusters. [This paper was published in: "Proceedings of the 44th Conference of the International Group for the Psychology of Mathematics Education, Vol. 2," edited by M. Inprasitha, N. Changsri, and N. Boonsena, PME, 2021, pp.57-64.]