This paper evaluates the effects of a multi-year program implemented in Spain between 2005 and 2012 which offered remedial education for underperforming students from poor socioeconomic backgrounds. We analyze the effect of this remedial program on students’ academic achievement by using external evaluations, in particular, the students’ scores in PISA 2012. We use two different estimation strategies: re-weighting estimators and propensity score matching. We find that PAE had a substantial positive effect on children academic achievement: the probability of falling behind the bottom part of the distribution reduces about 4% by receiving remedial education. In addition it improves mean reading scores by about 10% of one standard deviation.We find that a larger exposure to the program improves students’ scores: whereas implementing PAE during 1 or 2 years has almost no impact on students’ scores, implementing it during 3 or 4 years has so: it improves reading scores by about 13% of one standard deviation. The impact of the program in urban schools is much lower than in rural schools (about 15.8 PISA points, 0.18 standard deviations).