Is retention beneficial to low-achieving students? Evidence from Portugal

The role of retention as an educational tool to overcome under-achievement is a hotly debated issue, especially given that the results in the literature are not consensual. The Portuguese case is particularly well suited to study this issue: all students must take standardized national exams at specific grades. Moreover, the available dataset tracks the performance of students over time. Therefore, we are able to measure the impact of students' retention on their subsequent academic performance since we can control for each student's initial level of ability at the moment of retention. We use a propensity score matching approach, in which retained and promoted 4th grade students are matched according to their socioeconomic characteristics and the scores obtained in national exams. To address potentially remaining endogeneity biases, we also use the culture of retention at school level as an instrumental variable. The results suggest that in some situations retentions may have on average a positive impact on future achievement. However, in the cases where statistically significant impacts are found, the estimated magnitudes are relatively small. Our results are relevant for countries with high retention rates that are considering alternative educational policies to promote students' achievement.