„On average across OECD countries, the mathematics score attained by students who had attended pre-primary education for 1 year, 2 years or 3 years or more was higher (11, 17 and 16 score points higher, respectively) than the score attained by students who never attended or who had attended for less than one year, after accounting for socio-economic factors.“
OECD (Hrsg.), PISA 2022 Results, Vol.II. Learning During – and From – Disruption (2023), S. 134.