Student performance has been tested by various surveys at the international level in recent years, using different aims and methodologies. On the basis of a comparative analysis, this paper aims to describe the differences in performance between Italian regions, subjects and ages or grades. All the surveys revealed significant gaps in performance across the Italian regions, with students in the South being far behind those in the North in all the subjects surveyed (reading, mathematics, science). This gap is particularly marked in technical ("istituti tecnici") and vocational ("istituti professionali") schools. Also the degree of disparity in scores is higher in the South. The geographical divides increase with grade: the gaps between North and South are more mitigated at the earlier grades and concentrated among students with a low parental background. Student achievement is strongly correlated with the socio-cultural and economic conditions of the family. However, this relationship seems to be sharper at the earlier grades, while it vanishes at the upper secondary school level, when the type-of-program and school effects have much greater impact. Finally, this paper also suggests that marks (or final grades) given internally by schools do not reflect the real levels of proficiency, and do not, therefore, distinguish good students from bad ones.