An extensive body of studies has analyzed the effect of Mexico’s conditional cash transfer Oportunidades (former Progresa) finding important impacts on schooling outcomes, mainly in rural areas. However, most of the literature has focused on the program’s effects through demand-side factors, without analyzing the relevance of supply-side components. We attempt to measure the effect of differential exposure treatment of Oportunidades, when quality and endowment of education and health services differ across urban regions. The analysis centers on the upper-secondary level, in which drop out rates raise dramatically, thereby providing a wider margin to enhance the program’s performance. Our main findings reveal that this intervention policy boosts its impact when launched in areas with relatively low student-teacher ratios. Furthermore, we found that health quality, as well as school access, do matter for the program implementation, in contrast with the availability of health clinics, which has an ambiguous effect.