Peers matter but not always how we think

Creating classrooms that mix students of different ability levels and social backgrounds is often considered a key strategy to generate positive peer spillovers and reduce educational inequality. Yet, evidence shows that this assumption does not always hold true.

Most education systems – especially at the primary and lower secondary levels – promote classroom diversity to prevent segregation and to encourage students to benefit from each other’s differences. The underlying belief is that mixed classrooms foster inclusion, cooperation, and equity.

For decades, classroom formation practices were shaped by de facto or de jure segregation based on gender, socioeconomic background, or academic ability. Such divisions often translated into unequal learning opportunities. In the aftermath of World War II, and with the growing emphasis on freedom and civil rights, European education policies increasingly supported socioeconomic and ability diversity within schools.

Despite its popularity, the idea that classroom diversity automatically reduces inequality is far from universally supported by evidence. Some studies find that having classmates from higher socioeconomic backgrounds enhances learning outcomes. Perhaps because these students’ parents tend to be more engaged, monitor teaching quality, and exchange useful educational information. However, when it comes to ability diversity, the picture becomes more complex. The assumption that lower-achieving students will naturally assimilate the behaviours and performance of higher achieving peers, the so-called assimilation effect, is not consistently supported. On the contrary, several studies point to a big-fish-in-a-little-pond effect, in which exposure to more capable classmates lowers self-esteem and, consequently, leads to poorer academic performance and less ambitious educational choices.

Recent research in Italy, focusing on lower secondary schools, has investigated the causal impact of both ability-based and socioeconomic peer spillovers. The findings suggest that having a higher share of classmates with well-educated or affluent parents has a consistently positive effect. In contrast, the ability peer effect appears slightly negative, indicating that negative comparison mechanisms may take hold. 

These results are important. They do not call for abandoning the principle of heterogeneous classroom composition – since the combined effect of ability and socioeconomic diversity remains, overall, positive. However, they highlight the need to acknowledge and manage the unintended consequences of peer comparison. Teachers, in particular, play a crucial role in counteracting negative comparison dynamics and ensuring that classroom diversity truly translates into educational equity rather than hidden hierarchies.

Note
Funded by the European Union’s Horizon Europe Programme HORIZON-CL2-2023-TRANSFORMATIONS-01 Grant Agreement 101132531 and co-funded by UK Research and Innovation (UKRI) grant agreement numbers 10107302, 10092247 and the Swiss State Secretariat for Education, Research and Innovation (SERI).
 
Views and opinions expressed are those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them.

Dr Emanuele Fedeli

Produced and edited by Dr Doris Hanappi, Medea Fitzlaff MA, Miriam Daepp, Jacobs Center for Productive Youth Development

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