Over the past few decades, the figure of the market has clearly made its way into the field of education. For some authors, it represents an alternative to regulation by the public authorities, a different form of co-ordination which is better able to meet the objectives of the education systems. Through a secondary analysis of the PISA 2006 database, we test this hypothesis, as well as an alternative one which suggests that the quasi-market, rather than being linked positively to effectiveness of the education systems, would be associated with the students' achievement dependence on their socio-economic and cultural background and on the social composition of the school they are enrolled in. Our findings suggest that the quasi-market regulation (school autonomy and competition for student recruitment) (1) is not linked to effectiveness and (2) tends to be associated with a stronger link between schools' social composition and student achievement.