This study examined whether peer norms for aggression within the classroom impact friendship selection, maintenance, and socialization processes related to aggression across the 1st year of secondary school (N = 1,134 students from 51 classes, M = 12.66). As hypothesized, longitudinal social network analyses indicated that friendship selection and influence processes related to aggression depended on the popularity norm within the classroom (i.e., the class-level association between popularity and aggression) rather than the descriptive norm (aggregated average of aggressive behavior). Hence, only in classes where the valence of aggression is high (because it is positively associated with popularity), adolescents tend to select their friends based on similarity in aggression and adopt the aggressive behavior of their friends.

This longitudinal study examined the extent to which the development of prosocial and aggressive peer norms was related to individual prosocial and aggressive behavior development across the first year of secondary education (three waves, n = 1,134 adolescents from 51 classes, Mage = 12.66). A distinction was made between descriptive norms (the aggregated average peer-perceived behavior within the classroom) and status norms (the within-classroom correlation between peer-perceived popularity and behavior). Results indicated that descriptive norms represented a stable, static peer ecology, whereas status norms were somewhat more dynamic and changed across the school year. The development of descriptive and status norms was associated with initial levels of individual prosocial and aggressive behavior, whereas the development of status norms was also associated with the development of prosocial behavior.

Bullying among youth at school continues to be a global challenge. Being exposed to bullying may be especially hurtful in adolescence, a vulnerable period during which both peer group belonging and status become key concerns. In the current review, we first summarize the effectiveness of the solutions that were offered a decade ago in the form of anti-bullying programs. We proceed by highlighting some intriguing challenges concomitant to, or emerging from these solutions, focusing especially on their relevance during adolescence. These challenges are related to (1) the relatively weak, and highly variable effects of anti-bullying programs, (2) the complex associations among bullying, victimization, and social status, (3) the questions raised regarding the beneficial (or possibly iatrogenic) effects of peer defending, and (4) the healthy context paradox, that is, the phenomenon of remaining or emerging victims being worse off in contexts where the average levels of victimization decrease. We end by providing some suggestions for the next decade of research in the area of bullying prevention among adolescents.

This research investigated whether classroom-based peer norms for achievement goals moderate friendship selection, maintenance and influence processes related to academic achievement in 46 Grade 5 and Grade 6 classrooms (N = 901, 58.7% Grade 5 students, 48.5% boys). A distinction was made between peer norms for mastery (i.e., developing competence) and performance (i.e., demonstrating competence) goals. Peer norms were measured in terms of popularity norms (the within-classroom correlation between student achievement goals and popularity) and descriptive norms (the class-level aggregated average achievement goals). As hypothesized, longitudinal social network analyses revealed that achievement goal popularity norms played a role in friendship processes, rather than achievement goal descriptive norms. Specifically, adolescents formed friendships with similarly achieving peers in classrooms with high performance goal popularity norms but not in classrooms with low performance goal popularity norms. Conversely, adolescents remained friends with similarly achieving peers in classrooms with low performance goal popularity norms but not in classrooms with high performance goal popularity norms. Furthermore, friendship influence on achievement took place in classrooms with high mastery goal popularity norms, but not in classrooms with low mastery goal popularity norms. This study indicates that friendship processes regarding achievement depend upon the extent to which certain achievement goals are made salient by virtue of their association with popularity in classrooms.

Research on school bullying often focuses on the directional path of bullying and/or victimization leading to psychosocial problems, while such one-dimensional views have been shown to be too simplistic. Furthermore, recent research has shown that patterns of bullying at school differ for boys and girls, which makes gender a particularly relevant factor in exploring the causes and consequences of bullying. Therefore, the present study explored the bidirectional, longitudinal associations of bullying and bullying victimization on several psychosocial problems via a longitudinal cross-lagged panel study in 1243 adolescents in the Netherlands, while taking into account potential gender differences. Data were collected in September 2011 and 2012. Results showed that both bullied boys as well as girls reported more conduct problems at follow-up. Both boy and girl bullies reported less pro-social behavior and more peer problems at follow-up, but boys also reported more conduct problems at follow-up, while girls did not. Furthermore, in girls, emotional problems were associated with more victimization at follow-up, while inattention-hyperactivity problems and less pro-social behavior were related to increased chances of being a perpetrator of bully at follow-up. Conversely, in boys, baseline inattention-hyperactivity problems were not associated with being a bully later on, but rather with increased chances of being a bullying victim at later times. These results can help to tailor future anti-bullying interventions at schools.

School-based health-promoting interventions show promising results in improving various health outcomes of adolescents. Unfortunately, much is still unknown about the relations between health behaviors and school performances, while improving these would give schools a stronger incentive to invest in health promotion. This paper presents the associations of several health behaviors with school performances and studies the mediating effects of psychosocial problems. Health behavior and socio-demographic data were gathered from 905 Dutch high school students via an online survey, completed in-class. These data were matched with school records of the students' overall grade average (GA) on the three core subjects in Dutch high schools (Dutch, English and Math). The associations between health behaviors and school performances, and the potentially mediating effects of psychosocial problems, were studied via mixed-effects regression models. Smoking, being bullied, compulsive and excessive internet use and low physical activity were directly associated with lower school grades. Additionally, being bullied, bullying, smoking, excessive and compulsive internet use were associated with students' grades via mediation of psychosocial problems. This means that lower school grades were (also) associated with those behaviors through the effects of psychosocial problems in those students. This study showed the strong links between health behaviors and academic achievements among adolescents. Schools and health promoters should be educated more on these relations, so that they are aware of this common interest to get more support for health-promoting interventions. Additionally, the role of psychosocial problems in the relations between behaviors and school performances should be studied further in future research.

Objective: As empathy is an important predictor of both bullying and defending behavior, many anti-bullying interventions aim to increase empathy among students. However, little is known on whether these interventions enhance both affective and cognitive empathy, and whether some students are more responsive than others to empathy-raising efforts. This study examined the effects of the Finnish anti-bullying program KiVa on changes in self-reported affective and cognitive empathy and tested whether these effects varied depending on students' gender, initial levels of empathy, peer-reported bullying, and peer-perceived popularity, as well as school type (primary versus secondary school) and classroom bullying norms. Method: Multilevel structural equation modeling analyses were conducted on pretest and posttest (1 year later) data from a sample of 15,403 children and adolescents (Mage = 13.4; 51.5% girls) in 399 control and 462 intervention classrooms from 140 schools participating in the evaluation of KiVa in 2007-2009. Results: KiVa had a positive effect on affective empathy, but not cognitive empathy. The effects of the program on both types of empathy did not depend on students' gender, initial levels of empathy, bullying, or popularity, nor on school type or classroom bullying norms. Conclusion: Findings suggest that KiVa can raise students' affective empathy regardless of students' gender, status, initial empathy, or levels of bullying, and regardless of school type or classroom bullying norms.

Prior work has shown that popular peers can set a powerful norm for the valence and salience of aggression in adolescent classrooms, which enhances aggressive friendship processes (selection, maintenance, influence). It is unknown, however, whether popular peers also set a norm for prosocial behavior that can buffer against aggressive friendship processes and stimulate prosocial friendship processes. This study examined the role of prosocial and aggressive popularity norm combinations in prosocial and aggressive friendship processes. Three waves of peer-nominated data were collected in the firstand second year of secondary school (N = 1816 students; 81 classrooms; M age = 13.06; 50.5% girl). Longitudinal social network analyses indicate that prosocial popularity norms have most power to affect both prosocial and aggressive friendship processes when aggressive popularity norms are non-present. In prosocial classrooms (low aggressive and high prosocial popularity norms), friendship maintenance based on prosocial behavior is enhanced, whereas aggressive friendship processes are largely mitigated. Instead, when aggressive popularity norms are equally strong as prosocial norms (mixed classrooms) or even stronger than prosocial norms (aggressive classrooms), aggression is more important for friendship processes than prosocial behavior. These findings show that the prosocial behavior of popular peers may only buffer against aggressive friendship processes and stimulate prosocial friendship processes if these popular peers (or other popular peers in the classroom) abstain from aggression.