Although Flanders has a tracked education system, in PISA2003 our 15-year-old students' mean performance in mathematical literacy was the highest of all participating countries. In this paper we will try to explain this performance through secondary analysis on the item-level of the PISA2003 dataset. The focus lies in particular on the competencies the PISA-items require to be employed and on the four content areas of mathematics PISA distinguishes (i.e. space and shape, change and relationship, quantity and uncertainty). By looking at how our various student subgroups perform in relation to those two dimensions it's possible to provide an overview of the Flemish students' mathematical abilities.As a second step the Flemish profiles are compared to the profiles of students from some neighbouring countries with a similar education system (e.g. The Netherlands, Germany).Finally we will try to explain the Flemish results by linking them to the national maths curriculum and some typical educational practices.Research questionHow can the Flemish mean performance in mathematical literacy be explained? (What effect do the tracked educational system and the national maths curriculum have on the mathematical performance of Flemish students?) ReferencesDe Meyer, I. e.a.(2005), Learning for tomorrow's Problems in Flanders - First results from PISA2003. Ghent University, Ghent. OECD (2004), Learning for tomorrow's world - First results from PISA2003, OECD, Paris.