This is interesting, although do bear in mind that PISA only allows for claims about correlations, the data doesn’t allow to show any causal relations: students who have repeated a grade have higher risks of being victims of bullying in countries around the world, according to a new study of nearly half a million students.

From the press release:

Addressing and preventing school violence, including bullying, is a specific target of the United National Sustainable Development Goals. Few studies involving large samples have examined the association between grade repetition and bullying victimization. In the new study, researchers used data from the Program for International Student Assessment (PISA) 2018, which included information on 465,146 students aged 15 and 16 from 74 countries/economies.

Overall, 12.25% of included students had repeated a grade and 30.32% of students reported having experienced bullying at least a few times a month during the previous year. Students who had repeated a grade were more likely to have been the victim of bullying compared to their peers (OR 95% CI 1.32-1.52, p<0.001). The association was observed for students in 46 different countries/economies, and in students of both sexes. Compared to boys, however, girls who repeated a grade had higher risks of being made fun of, being threatened, having possessions taken away, and being pushed around.

The authors note that while the findings support a relationship between the experiences of repeating a grade and bullying victimization, the cross-sectional study cannot determine if such a relationship is causal, or the direction of the relationship. The study was also limited to adolescents who were attending school at the time the survey was administered, and the measures of bullying experiences and grade repetition were self-reported.

“These results are of great concern for parents, teachers, principals, and policymakers at different levels, especially in countries where grade repetition is particularly prevalent,” the authors say. “Grade repetition is associated with bullying victimization in both boys and girls.”

Background
Grade repetition is practiced worldwide and varies considerably across the globe. Globally, around 32.2 million students repeated a grade at the primary education level in 2010. Although a large body of research has documented grade repetition’s academic and non-academic effects, the limited evidence on associations between grade repetition and school bullying is inconsistent and ambiguous. This study aimed to investigate the global association of grade repetition with bullying victimization in a large-scale school-based cross-sectional study.

Methods and findings
We used the latest global data from the Program for International Student Assessment (PISA) 2018. PISA 2018 was conducted between March and August 2018 in 80 countries and economies among students aged 15–16 years attending secondary education. The students reported their experiences of repeating a grade at any time point before the survey and of being bullied in the past 12 months. The outcome measures were 6 types of bullying victimization. We accounted for the complex survey design and used multivariate logistic regression models to estimate the odds ratios (ORs) with 95% confidence intervals (CIs) of grade repetition with bullying victimization after adjusting for potential confounders (sex; age group; migrant status; school type; economic, social, and cultural status; and parental emotional support). This study included 465,146 students (234,218 girls and 230,928 boys) with complete data on grade repetition and bullying victimization in 74 countries and economies. The lifetime prevalence of grade repetition was 12.26%, and 30.32% of students experienced bullying at least a few times a month during the past 12 months. Grade repetition was statistically significantly associated with each type of bullying victimization. The OR (95% CI) of overall bullying victimization for grade repeaters compared with their promoted peers was 1.42 (95% CI 1.32–1.52, p < 0.001). The sex-specific analysis produced similar results in both boys and girls. Furthermore, girls who repeated a grade had higher risks of being made fun of, being threatened, having possessions taken away, and being pushed around than boys. The major limitation is that this study only included students attending schools and therefore may be subject to possible selection bias. In addition, the cross-sectional design hinders us from establishing causality between grade repetition and bullying victimization.

Conclusions
In this study, we observed that, globally, both boys and girls who repeat a grade are at increased risk of being bullied compared with promoted peers, but girls may experience higher risks than boys of specific types of bullying associated with repeating a grade. These findings provide evidence for the association of grade repetition with bullying victimization. Sex differences in risk of experiencing some types of bullying suggest that tailored interventions for girls who repeat a grade may be warranted.