Introduction: Assertive behavior is the ability to communicate the individual's want, feel, and think to others honestly and openly while respecting personal and other people's rights. One way to increase assertiveness in adolescents is through assertive training activities where this activity presents systematic activities that can develop and train individuals' abilities to express their thoughts, feelings, desires, and needs confidently. The purpose of this study was to analyze the change in assertive behavior of adolescents living in Islamic boarding schools through assertive training.Method: This was pre-experimental research with pre-post design.  The sample was 80 respondents which were obtained by the purposive sampling technique. The measuring instrument uses assertive behavior questionnaires and data analysis using the Wilcoxon Paired testResults: The results of the analysis of assertive behavior in adolescents before the intervention were in a low category (42.5%) and after the intervention, adolescent assertive behavior was in a good category (46.3%). The results showed a p-value of 000 which is result indicated that there was an increase in the assertive behavior of adolescents living in Islamic boarding schools through assertive training.Conclusions: Adolescents with high assertiveness are able to control their emotions, mental health and have good coping with solving personal and social problems, and are able to express their wishes firmly to others

Aggressive as physical or verbal behavior intended to cause harm. Meanwhile, aggressive behavior is a serious problem that has a negative impact on adolescent mental health and achievement in school. The purpose of this study was to describe aggressive behavior in adolescents in high school environments in urban and rural areas of Jember Regency. The design of this research is a quantitative descriptive research. This research was conducted in senior high schools in rural and urban areas in Jember Regency with a total sample of 250 respondents who were selected using a purposive sampling method. This study used univariate analysis, wherein the results of this study will display demographic data and a description of aggressive behavior in adolescents. The results of the emotion study showed that 46.4% of respondents had verbally aggressive behavior, 29.6% of respondents had physically aggressive behavior, 12.8% of respondents had angry aggressive behavior and 11.2% of respondents had hostile aggressive behavior. Based on the results of this study that the aggressive behavior of adolescents tends to be high, so to overcome aggressive behavior in adolescents it is necessary to make various efforts by paying attention to the dimensions of development in adolescence so that the efforts developed are able to overcome various causes of mental health problems faced by adolescents and adolescents have resilience..