This proportion is particularly high in Belgium, France, Luxembourg, Portugal and Spain, where it affects over 30% of students. In these countries, repetition has been one of the main tools to respond to individual weak performance and preserve an even level of attainment within each classroom. A study based on PISA 2009 data found that, in about half of the countries examined, students' socio-economic status is related to the likelihood of repeating a grade, even after accounting for student academic performance (Monseur and Lafontaine, 2012). In fact, data from PISA 2009 revealed, among OECD countries, 53% of the variation in the likelihood of a student repeating a primary grade is observed at the student level, 28% at the school level, and 19% at the system level (Coos et al., Teachers widely support grade repetition, as they can see the immediate gains in going over the same curriculum a second time (Jimerson, Anderson and Whipple, 2002).