Bullying and victimization among children and adolescents remain central concerns for educational research and school practice, with substantial implications for psychosocial development and educational trajectories. Contemporary research increasingly conceptualizes bullying as a group process involving multiple participant roles like bullies, assistants, victims, defenders, and outsiders (Jenkins et al., 2022). However, bullying research faces persistent challenges in measurement. Self-reports, although widely used due to their efficiency (Paljakka et al., 2021), are prone to social desirability and underreporting biases, particularly when assessing socially undesirable behaviors such as bullying perpetration and when children feel uncomfortable reporting victimization (Bouman et al., 2012). Building on the participant role model and social-ecological perspectives, bullying is understood as embedded in peer group interactions and classroom social structures. This implies that peers are key informants of classroom social dynamics (Salmivalli et al., 2021). In addition, bullying behaviors are assumed to be publicly observable and strategically enacted in peer contexts, making classmates important observers of these processes (Rodkin et al., 2015). From a measurement perspective, peer-reports complement self-reports by capturing shared perceptions of social roles and group dynamics. Yet, existing peer-rating instruments often require students to evaluate numerous classmates across multiple items, which imposes substantial cognitive demands and limits feasibility in school-based research (Vessey et al., 2014). Integrating insights from bullying research and educational measurement theory, this contribution addresses the need for theoretically grounded and feasible approaches to assess participation in bullying roles. Increasing emphasis on scalable indicators and data-driven approaches highlights the need for instruments that balance feasibility with conceptual depth and contextual sensitivity. Developing parsimonious yet theory-based measures can support cumulative research and evidence-informed educational practice. The submitted poster aims to present and theoretically ground the Single-Item Peer-Rating for Bullying Participation Roles (SIPER-BPR) and to outline the conceptual framework for its evaluation. SIPER-BPR is designed as a parsimonious peer-based instrument to capture students’ participation in bullying-related roles in classroom contexts. The poster will introduce the conceptual rationale of the instrument and outline research questions regarding descriptive characteristics of peer-reported roles, convergence with self-reported role involvement, and associations with psychosocial indicators. We assume small to moderate correlations between peer- and self-reported role involvement (Malamut et al., 2020), reflecting shared variance and method-specific biases, and theoretically expected associations with social and behavioral characteristics (Moyano et al., 2019).

The study involved N = 1688 students (M = 11.55 years, SD = 1.11; 52% female) from 80 classes spanning grades 5 through 9, as well as their classroom teachers (N = 80; M = 41.4 years, SD = 8.77; 66% female) in Germany. Data collection occurred at two measurement points with a six-week interval. Participation in bullying roles was assessed via SIPER-BPR and the Bully Participant Behavior Questionnaire (BPBQ; Eilts et al., 2025). The SIPER-BPR is designed to capture the participation of classmates in five bullying-related roles: bully, assistant, victim, defender, and outsider. Each role is represented by a single item describing observable behaviors within the classroom (e.g. Bully: “In many classes, there are children who intentionally and repeatedly hurt weaker children or are mean to them. For example: They insult others. They exclude others. They hit or push others. They throw things at others. They say mean things about others.”). Peers rated the frequency of the corresponding behavior on a seven-point Likert-like scale for all of their classmates, allowing aggregation of perceptions and capturing classroom-level social dynamics. Students’ self-reported bullying behavior was assessed using the German short version of the BPBQ, which captures the frequency of aggressive behaviors in peer contexts. Students’ self-perceived social integration was measured using the subscales “Negative Interactions” and “Exclusion” of the Questionnaire for Multifactorial Assessment of Self-Perceived Social Integration (SSI 5-6; Spilles et al., 2025). Peer-reported social integration was assessed via sociometric choice (Moreno, 1934) capturing students’ acceptance within the classroom social network. Anxious-depressive and oppositional-disruptive behavior was assessed using the respective subscales of the Integrated Teacher Report Form (ITRF; Casale et al., 2023). Teachers also provided a global assessment of students’ behavioral support needs using a single five-point item as a proxy variable. Data collection was conducted in classroom settings during regular school hours at both measurement points. The research objectives were addressed by analyzing the data using correlation coefficients.

The findings indicate that peer-ratings capture the theoretically expected role-specific patterns and offer added value beyond student self-reports, supporting the instrument’s potential as a low-burden, scalable measurement tool for research and practice. Correlations between peer-ratings (SIPER-BPR) and the self-reported behavior (BPBQ) ranged from r = .213 for Defenders to r = .447 for Bullies. These coefficients are comparable to prior research reporting modest cross-informant agreement in bullying research and reflect the well-documented divergence between self- and peer-reports in socially sensitive behaviors. Evidence for construct and criterion-related validity emerged from the role-specific associations with relevant student characteristics. Peer-rated Bullies and Assistants showed moderate to strong positive associations with oppositional-disruptive behavior and teacher-rated behavioral problems, and smaller but still significant associations with anxious-depressive symptoms. Victims were characterized by higher levels of internalizing problems and lower social integration. Defenders showed positive associations with peer-reported social integration and negative associations with behavioral problems, whereas Outsiders were associated with lower social integration and higher behavioral problems. Importantly, these patterns were generally stronger for peer-ratings than for self-reports, suggesting higher external validity of peer-based assessments for capturing social roles within classrooms. Still, differentiation between Bully and Assistant roles remains challenging and warrants further refinement of item wording. Nevertheless, the results indicate that the single-item peer-rating approach differentiates bullying roles in theoretically meaningful ways and aligns with established nomological networks. Due to its low assessment burden, the instrument is a scalable measurement tool for research and practice. Further research is needed to examine its reliability over time and in different contexts.

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