In this paper we estimate the impact of a nationwide public preschool expansion that took place in Spain over the 1990s on criminal behavior later in time. We exploit variation in enrollment rates across Spanish regions and birth-cohorts, and we link education data to a unique administrative crime dataset recording offenses committed in the region of Catalonia over the period 2009-2014. We find that for the average birth cohort, Catalan municipality and year, a 1 percentage point increase in preschool exposure at age 3 yields 1.6% fewer crime actions during youth and young adulthood.