School-sector differences in student performance are often viewed as largely reflecting the intake characteristics of students and having little to do with differences in the provision of teaching and learning between school sectors. The contrary view is that school-sector differences show that non-government schools "add value" to student performance through their delivery of the curriculum. This paper analyses tertiary performance (ENTER scores) among students who participated in the 2003 PISA study. It examines the extent to which school-sector differences are accounted for by students' socio-economic background, prior achievement, and various aspects of student learning. It concludes that sector gaps in students' tertiary entrance performance can be only partially attributed to socio-economic background and there are moderate value-added effects for school sector when taking into account students' prior achievement. Although aspects of student learning had important effects on ENTER scores, they generally did not further account for school-sector differences. Further analyses suggest that non-government schools promote a more academic environment that lifts student performance. This finding has policy implications for all sectors. (Contains 3 notes and 6 tables.)