Comprehensive education until the end of lower secondary education allows temporary grouping of students by ability in core subjects such as mathematics or language. The proportion of students enrolled in privately managed schools is above the OECD average. While this can widen inequities, policies to promote more balanced distribution are in place to ensure that students with low socio-economic status have opportunities to attend their preferred school. Grade repetition is also largely used: about one out of three students (35%) have repeated a grade at least once by age 15.