This working paper reviews key findings from empirical research on the effects of specific modes of privatization of the school provision, particularly in developing countries. The overall question is: can the common good of education be provided by the private sector in a more efficient or optimal way than by the state? The paper presents first a definition of privatization. It then elaborates on the multiple modes that privatization may take in the schools sector in relation to diverse policy goals and reviews findings from prior research on this isseu. Third, it discusses some methodological issues that commonly arise when reviewing international evidence. Finally, the paper presents a synthesis of findings and offers lessons learned particularly intended for policy-makers, planners, and administrators.