Educational public-private partnerships (EPPPs) promise to increase education access and quality in developing countries, provided they have an adequate design that restricts the distribution of subsidies including targeted programs, centralized controlled enrolment, and accountability. This study investigates the effects of publicly subsidized private schools (PSPS) in Colombia--a type of EPPP program that follows all of these recommendations. We use propensity score and regression techniques to identify PSPS effects on student achievement, measured by national standardized tests. Our results show that Colombian PSPS serve vulnerable students, who are fairly similar to those attending traditional public schools (TPS). Nevertheless, students at PSPS underperform compared to TPS students. Our conclusion suggests that design restrictions may prevent student selection and self-selection, but do not guarantee quality improvement for disadvantaged students at subsidized schools. We also argue that design restrictions for PSPS may not be enough when private providers are scarce or difficult to attract for serving the most disadvantaged population.