„On average across OECD countries, the mean reading score of students who had attended pre-primary education for one year (471 points), two years (491 points) or three years or more (493 points) was higher than the score of students who had not attended or had attended for less than one year (444 points).“
OECD (Hrsg.), PISA 2018 Results. Effective Policies, Successful Schools (2020), S. 51.