This paper studies the effect of a civil service reform on the skills profile of new teachers in Mexico. The reform mandated the use of rule-based recruitment over discretionary hiring. Our results show that the reform led to hiring teachers with higher cognitive skills. We also show that an improvement in the bottom of the skills distribution of new hires drove this change. Two channels explain these effects. First, the reform decreased the prevalence of discretionary hires, who tended to be drawn from the bot tom of the skills distribution. Second, the reform improved the screening efficiency of rule-based hiring, making cognitive skills more important determinants of hiring outcomes.