Students who had attended pre-primary school for at least one year …

„PISA 2022 results clearly show that, on average across OECD countries and in a majority of education systems, students who had attended pre-primary school for at least one year were considerably less likely to have repeated a grade at any education level than students who had never attended pre-primary school or who had attended for less than a year, even after accounting for socio-economic factors.“
OECD (Hrsg.), PISA 2022 Results, Vol.II. Learning During – and From – Disruption (2023), S. 258.