This paper evaluates the e¤ects of a remedial education programme implemented in Spain between 2005 and 2012 that o¤ered after-school classes for underperforming students from poor socioeconomic backgrounds. We use two di¤erent estimation strategies, re-weighting estimators and propensity score matching, and address the existence of selection bias. We …nd that this programme had a substantial positive e¤ect on children's academic achievement: the probability of falling behind the general progress of the group declined by approximately 5% and mean reading scores increased by approximately 10% of one standard deviation. We also …nd that a larger exposure to the programme improves students'scores: whereas students in schools that participated in the programme for at most two years do not experience any signi…cant positive e¤ect, those in schools that participated for at least three years did. The programme signi…cantly reduced the probability of belonging to the bottom part of the distribution (by approximately 7.5%) and improved mean scores (by approximately 18% of one standard deviation). Finally, we …nd that the impact of the programme is much stronger for students in rural schools than for students in urban schools.