We analyze the impact of longer school schedules on children’s early reading skills in Chile. We make use of the first 2nd grade SIMCE to measure early reading skills. Since families choose schools in Chile, we identify the causal effect of the full day policy with instrumental variables, using the local availability of full-day schools and full-day 1st and 2nd grade as an instrument. We find that, controlling for selection, longer school schedules lead to an increase of 0.2 standard deviations in reading skills. We also find that the effects are heterogeneous, with greater benefits among children in municipal schools and girls.