Defending in bullying is a complex, yet important behavior that is likely associated with individual characteristics and group factors that operate simultaneously in the classroom microsystem. However, little research has longitudinally analyzed the role of multiple promoting factors at both the individual and classroom level. Drawing on the social-ecological theory and social-cognitive theory, the present study examined the prospective associations between Fall defending self-efficacy, moral disengagement, moral identity, and moral distress and Spring defending behavior. Participants were 1163 adolescents (48.7% females; M_age = 13.6, SD = 1.1) attending 67 classrooms in Italian public schools. Defending showed moderate stability over one school year. At the individual level, multilevel analyses showed that T1 self-efficacy for all students, and moral distress for male students, positively predicted T2 defending. Moreover, high moral disengagement negatively predicted T2 defending only when students also reported high levels of moral identity. At the class-level, T1 class defending and class moral identity explained between-class variability in T2 defending. The findings have multiple implications for interventions that aim to increase defending behavior.

在欺凌中进行辩护是一种复杂但重要的行为，它可能与在课堂微系统中同时发挥作用的个人特征和群体因素有关。然而，很少有研究纵向分析多个促进因素在个人和课堂层面的作用。本研究借鉴社会生态理论和社会认知理论，研究了秋季防御自我效能、道德脱离、道德认同和道德困扰与春季防御行为之间的前瞻性关联。参与者为 1163 名青少年（48.7% 为女性；M_年龄 = 13.6，SD = 1.1) 参加意大利公立学校的 67 间教室。防守在一学年中表现出适度的稳定性。在个人层面，多层次分析表明，所有学生的 T1 自我效能感和男学生的道德困扰，正向预测 T2 防御。此外，只有当学生也报告了高水平的道德认同时，高道德脱离接触才能负面预测 T2 防守。在阶级层面，T1 阶级防御和阶级道德认同解释了 T2 防御的阶级间变异性。这些发现对旨在增加防御行为的干预措施具有多重意义。