Background
School injuries are a key public health problem [
1‐
5]. Injuries are the leading cause of adolescent mortality [
6‐
9], and even non-fatal injuries have several detriments, such as temporary or permanent disabilities [
3,
10‐
12]. These consequences entail a deterioration in well-being and an increase in school absenteeism, potentially lowering academic achievement of affected students [
3,
13‐
15]. Studies reveal that about 25 percent of all injuries to children under the age of 17 occur at school [
5,
9,
16‐
21]. For Germany, the social accident insurance reports that in 2019, a total of 1.17 million school injuries required medical treatment [
1]. Adolescent students are particularly vulnerable to school injuries, compared to both older and younger students [
3,
9,
20,
21].
Despite the prevalence and consequences of adolescent school injuries, knowledge on specific risk factors remains limited. In general, the literature attributes school injuries among adolescents to the increase in risk-taking and violent behavior during adolescence [
9,
22,
23] These crucial risk behaviors for adolescent school injuries are closely associated with peer effects [
24‐
30]. However, peer contexts have rarely been considered in the literature on school injuries so far. Previous studies have relied on medical record data to investigate patterns among injured students [
3,
5,
9,
12,
20,
31]. However, injury records lack information on non-injured counterfactuals, inhibiting analyses of factors that might foster or prevent school injuries. A few studies have analyzed data on both injured and non-injured students, but focused on selected individual-level risk factors or the physical environment at schools [
4,
23,
32,
33].
In this paper, we focus on the potential role of classroom sex compositions for adolescent school injuries to add a contextual perspective on school injuries. A contextual perspective on adolescent school injuries is essential because both key risk factors – risk-taking and aggression – are largely a group phenomenon. Adolescents spend more time with their peers and exhibit the highest level of concern with being accepted in relevant peer contexts than any other age group [
34,
35]. The crucial role of peer contexts for adolescents particularly concerns effects on risk-taking and aggression, since both behaviors disproportionately occur when adolescents are with their peers [
36,
37]. An extensive body of literature documents that peer norms and behavior patterns of peers are a primary contextual factor for adolescent risk-taking, violence, and aggression [
27‐
29,
34,
37‐
40]. Classmates constitute important peer contexts because adolescent students spend around 50% of their waking hours in school [
41]. Classroom norms and social ties within these contexts create peer pressure towards or away from risky or aggressive behavior, and adolescents are particularly susceptible to these peer group dynamics: adolescents, particularly boys, are more likely to engage in risky behavior and aggression when classroom peers display such behavior [
25,
42]. Thus, given the importance of risk-taking and aggression for adolescent school injuries, classroom peer contexts constitute a crucial aspect in order to arrive at a better understanding of school injury risks.
A key source of contextual peer effects on adolescent school injury risks might be the sex composition of a classroom, i.e. the sex ratio of boys and girls in a class. Evidence from experiments and observational data suggests that aggression and risk-taking are associated with the sex ratio in a given context [
43‐
50]. The literature identifies male status thriving and competitive orientation as key sources for levels of physical aggression by men, including male adolescents [
51‐
53]. Adolescent boys exhibit a stronger orientation towards physical competition and domination than girls. Male adolescents are also more likely to consider physical aggression to be an effective means of attaining social status among peers [
24,
26,
51]. Empirical evidence suggests that this male tendency for physical rivalry is exacerbated in male-dominated contexts, resulting in higher levels of violence, particularly against other men [
43,
47,
48,
54‐
57]. For adolescents, previous research has demonstrated that peer effects on adolescent delinquency are contingent on the sex constellations of peers [
26,
30]. Moreover, higher levels of violence mediate the negative relationship between classroom shares of male students and academic performance in classes with high shares of male students [
58]. Similarly, exposure to female in-school peer contacts decreases adolescent males’ odds of engaging in serious violence, while having more male friends is associated with increased violence by girls [
24]. Evidence for sex ratio effects on risk-taking also exists. For instance, male-dominated contexts appear to instigate risk-taking in experimental [
44,
45,
59] and health-risky behavior in non-experimental studies [
49,
60].
This paper explores whether and how classroom sex ratios are related to school injury risks. Sex ratios have been shown to correlate with behavioral patterns that are relevant for school injury risks, however, the role of classroom sex constellations for school injury risks has not been explored yet. To examine this relationship, we use data from a large-scale longitudinal survey study on school injuries and health of adolescents in Germany [
61]. The results provide policy makers, school officials, and other stakeholders seeking to reduce violence and injuries in schools with a perspective that may offer ways in dealing these issues beyond individual interventions.
Discussion
In this paper, we use nationwide survey data from Germany to investigate the link between classroom sex ratios and adolescent school injuries. School injuries are a major public health problem with important implications for students’ quality of life and academic achievement [
2‐
4,
10,
13‐
15,
17,
18]. However, empirical evidence on contextual risk factors for adolescent school injuries has been lacking so far. This is despite the fact that key risk factors for adolescent school injuries – aggression and risk-taking – have consistently shown to be highly susceptible to contextual influences. Moreover, a growing body of literature suggests that male-skewed sex ratios increase adolescent risk-taking and in particular physical aggression [
24,
26,
30,
43,
44,
47‐
49,
54‐
59]. In this paper, we bring together these spheres of expertise to explore the role of classroom sex compositions as a contextual risk factor for adolescent school injuries.
Overall, our analysis reveals four main findings. First, we find that adolescents face higher risks of sustaining school injuries when they are part of a male-skewed classroom. Second, additional models suggest that boys’ and girls’ injury risks are similarly associated with the share of male students in a classroom. Third, the association between classroom sex ratios and injury risks is even more pronounced when we focus our analysis on only those injuries that are attributable to aggression by other students. Thus, students in male-skewed classroom contexts are more likely to report an aggression-related school injury. Fourth, both boys and girls are equally at higher risk of sustaining an aggression-related injury when they are part of a male-skewed classroom sex ratio.
Our findings illustrate the need to integrate a contextual perspective in research on school injuries, particularly among adolescents. Previous studies have emphasized the crucial role of school facilities, environmental factors, and individual characteristics of students for school injury risks [
4,
33]. Our results offer a complementary perspective by highlighting the social context of injury risks. This is not to downplay environmental risk factors such as weather, yard facilities, or architectural aspects for school injuries. However, the way students interact with these facilities and with one another is crucial for how likely these hazards translate into injuries. Contextual peer effects are particularly relevant for adolescents, including adolescent risk-behavior and aggression [
27‐
29,
34,
36‐
40]. Our results illustrate the specific relevance of the composition of peer contexts at school for adolescent school injuries.
Interventions to prevent adolescent school injuries should therefore also take into account the sex composition of classrooms. Ensuring a mix of boys and girls in classrooms could help reduce the number of school injuries. Moreover, interventions should target specifically male-dominated classes. The literature suggests that the increase in injury risks in male-skewed classrooms results from higher levels of risk-taking and aggression in male-skewed contexts [
24,
30,
43,
45,
47,
48,
54]. Both risk-taking and aggression have an important signaling function since it often confers status, particularly to adolescent males. Therefore, successful interventions should aim to specifically provide adolescents with alternative, safer forms of status attainment. Specifically, interventions should guide adolescents towards alternative means of gaining social acceptance and respect, where adolescents can attain status without contests or engaging in antisocial behavior [
67]. For instance, a recently proposed framework highlights how processes of learning and self-reflection helps to counteract the establishment of toxic masculinity norms related to antisocial behavior [
68].
This paper uses nationwide survey data with self-reports on school injuries, and analyses of such data come with certain limitations. Compared to studies relying on medical records, our data provide crucial information on the classroom context and information on non-injured students. However, information on school injuries is collected retrospectively, entailing the risk of recall error or recall bias. However, given that the survey focuses on severe injuries that required medical treatment, we expect that most affected students will be able to recall such a memorable event. A second limitation is that the aggression-related school injuries might not distinctly distinguishable from injuries resulting from other causes. In certain instances, injuries might be attributable to both third-party aggression as well as own risk-taking. Given that we find a similar association for both, all injuries and aggression-related injuries can, however, be considered as indicative of an overall association of sex ratios and injury risks. Moreover, while we can reconstruct classroom sex ratios, our data do not contain information on how closely students from a class interact with each other. Network approaches to peer effects frequently use directed friendship relations where students nominate their friends to reconstruct peer contexts for each student [
24,
26,
30,
40]. Such information would help to approximate closer the sex composition of students’ peers. Nevertheless, network-based approaches also suggest that not only close friends, but also more distal peers do affect behavior in profound ways [
40]. Consequently, our results constitute a baseline for a combined measure of sex compositions in close and distant peers at school. Finally, we cannot fully avoid problems of unobserved heterogeneity between schools and classes from differential preferences of boys and girls with respect to STEM or liberal arts [
69]. However, we are able to attenuate this problem by adjusting for time-invariant unobserved characteristics of school classes by including random intercepts at the class-level.
Finally, further research is needed to clarify the mechanisms behind the link between classroom sex ratios and injury risks from risk-taking and aggression. Generally, the literature either draws upon biological differences between the sexes or gender-specific social expectations to explain sex ratio effects in behavior [
70,
71]. While these approaches differ in their theoretical frameworks, both identify male status thriving and competitive orientation as prime sources for higher male involvement in physical aggression and health-detrimental risk-taking [
51‐
53]. However, we acknowledge that we are not able to adjudicate on such pathways based on our results. In particular, our data do not contain information on aggressors. Therefore, we cannot establish whether a male-skewed classroom sex ratio instigates aggression primarily by male or female students. The literature on sex ratio effects on violent offending primarily focuses on male offenders [
47,
48,
72,
73]. Yet, there is evidence that female violence also increases when sex ratios are male-skewed. In particular, research shows that girls’ delinquency is higher if they affiliate with male friends [
74‐
76] and that having more male friends is associated with more antisocial behavior in girls [
24,
77]. Thus, the lack of information on offenders prevents us from establishing whether the surplus injuries from aggression are actually driven by
male aggression. Future studies should consider collecting details on the aggressor(s) to further explore the underlying mechanisms. Moreover, qualitative observational studies of peer dynamics or in-depth interviews with adolescents about their experiences in different sex ratio contexts are necessary to identify the particular mechanisms at play.
Despite these limitations, there are numerous strengths of our study including the nationwide scope and longitudinal nature of our data. The details on the classroom context and information on non-injured students helps us to elucidate that sex ratios are an important contextual factor for adolescent injury risks. On a broader theoretical level, our findings support concerns that male-skewed sex ratios are associated with an increase in aggression and violence [
43,
47,
48,
54,
78,
79]. Additional research is needed that examines the underlying mechanisms how classroom sex ratios are associated with school injuries, specifically addressing the relation to aggression-related injuries. Nevertheless, this study provides a meaningful first step towards a more detailed exploration of school injury risks and classroom sex ratios as well as contextual effects in general.
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