The principal aim of this article is to describe and document a comparison of public and private school effectiveness in the marginalized (often referred to as slum) district of Aguablanca, in the city of Cali, Colombia. The data suggest that teachers and parents are largely satisfied with the current status of education provision in Aguablanca. However in terms of "statistically significant" differences, stakeholder perception of the private sector exceeds that of the public sector for every given indicator. The research suggests that the authorities reconsider their education strategy in light of the positive perceptions associated with the existing system of provision. While it may be necessary to increase system capacity in order to meet the demand, great care should be taken to protect (and even extend) provision for the poor through the existing programme of private school subsidies. (Contains 4 figures and 2 tables.)