„In horizontally stratified systems, students of different abilities, behaviour or interests are separated into different schools, programmes and classes so that what is learned (content and difficulty) and how it is taught (pedagogy) can be tailored to better meet students’ needs. This sorting and grouping of students is generally termed educational stratification, which refers to the various ways that schools and education systems organise instruction for students with different abilities, behaviour, interests and pace of learning.“
OECD (Hrsg.), PISA 2022 Results, Vol.II. Learning During – and From – Disruption (2023), S. 127.