Project 1.1

This PhD project investigates how social cohesion develops among youth in ethnically diverse schools. It traces how different cohesion dimensions – such as interethnic friendships, school attachment, trust in institutions and national identity – co-evolve. Do cohesion dimensions reinforce or hinder each other? Which dimensions correlate and which are unrelated? What role does ethnic diversity play in these associations? The PhD candidate will analyse large-scale survey data from Europe to study friendship networks, identity formation and school climates. These insights will inform a school-based intervention. The project offers theoretical innovation, novel empirical insights and practical tools for strengthening ethnic cohesion among youth.

This PhD project investigates how social cohesion develops among adolescents who attend ethnically diverse secondary schools. It traces how different cohesion dimensions, such as interethnic friendships, school attachment, trust in institutions and national identity, co-evolve. The project seeks to develop and test a multidimensional framework of social cohesion in the context of increasing ethnic diversity. In particular, the project seeks to uncover how dimensions along horizontal lines of cohesion (i.e., relationships between individuals and groups, such as friendships, intergroup attitudes and social rejection) connect to vertical lines of cohesion (i.e., ties between individuals and institutions, such as trust in the government, feelings of national belonging and school attachment) among youth. To this end, the project will analyse diverse school contexts and identify how school- and regional-level conditions strengthen or weaken these horizontal and vertical cohesion dimensions as well as the association between these two dimensions. It further aims to design and test an intervention that fosters positive spillovers between both dimensions and project how cohesion may evolve under changing demographic scenarios. Ultimately, the project aims to generate new theory, robust empirical insights and practical tools that help educators and policymakers strengthen cohesion among youth in a sustainable way.

This project draws on large-scale secondary survey datasets that capture the horizontal and vertical dimensions of social cohesion among youth in ethnically diverse school contexts. These data provide rich and partly longitudinal and cross-national information that enables us to examine how the horizontal and vertical dimensions of cohesion co-occur within and across schools.

The first dataset is the Children of Immigrants Longitudinal Survey in Four European Countries (CILS4EU), including approximately 18,000 adolescents from around 800 classrooms nested in 400 schools across Germany, the Netherlands, Sweden and England (2010–2017). The second is the Educational Monitoring Study (2022) conducted by the Institute for Educational Quality Improvement (IQB) at Humboldt University of Berlin, with around 1,300 classrooms of students across Germany. Both datasets contain extensive measures of horizontal ties (e.g., friendships, interethnic attitudes and networks) and vertical ties (e.g., school attachment, national belonging and trust in institutions), and they complement each other in terms of period, scope and measurement.

The analytical design follows the four steps of this project, applying different statistical techniques (multilevel modelling, meta-regression, social network analysis). First, it will examine the extent to which horizontal and vertical cohesion are related and assess the degree of heterogeneity across schools (step 1). Second, it will explain this variation by testing the role of factors such as school composition, diversity policies and broader contextual characteristics (step 2). Based on these insights, and in collaboration with stakeholders, the project will design and pilot school interventions aimed at strengthening cohesion, collecting experimental data in one to two schools to evaluate their impact (step 3). Finally, the project will integrate findings from the first three steps into simulation models that project how horizontal and vertical cohesion may evolve under different demographic and policy scenarios, such as increasing ethnic diversity or school segregation, based on simulation methods (step 4).