The gap is larger in countries that track students early, have larger percentages of students in selective schools, and are more likely to transfer less-able students to other schools. There is now a wealth of evidence, including longitudinal studies, that investing in ECEC yields high returns in boosting cognitive and non-cognitive skills, as well as later success in the labour market, especially for disadvantaged children (Heckman, 1999, Lazzari and Vandenbroeck, 2013). Children from socio-economically disadvantaged families in Belgium and Slovenia, for example, are given priority access to ECEC (OECD, 2012b).