„The striking stability in the SES gradients at age 6-8 and those at age 15 reported in PISA suggest that reducing inequalities prior to school entry may have far-reaching effects on social mobility. […] However, the case study of France reminds us that a note of caution is needed about focusing attention exclusively on environments in the early years. The strong French SES gradient in PISA suggests that the benefits for equality of its world-leading preschool system are completely eroded over the course of primary and lower secondary schooling, such that it ends up with an internationally high gradient by age 15, with a level similar to that in Germany.“
Dr. Jascha Dräger u. a., Cross-national differences in socioeconomic achievement inequality in early primary school: the role of parental education and income in six countries (2023), S. 28.