This paper aims at estimating the effect of private vs. public education on pupils' achievement using the 2000 Organisation for Economic Co-operation and Development (OECD) Program for International Student Assessment (PISA) survey and taking into account the potential bias due to the existence of unobserved confounding factors. To deal with these selection biases, three methods are implemented in a comparative perspective: (1) instrumental variable (IV) regression; (2) Heckman's two-stage approach and (3) propensity score matching. This exercise underlines important divergences between the results of parametric and non-parametric estimators. All results, however, show that private education does not generate systematic benefits.