This study aimed to examine student and school characteristics that could affect adolescents' social and emotional learning (SEL) skills. The study group consisted of randomly selected 3017 high school students from 42 schools in Turkey. According to two-level Hierarchical Linear Modelling analysis findings, the mean SEL scores of schools differed statistically significantly. The variables of academic achievement, participation in events (scientific, artistic, sports, community services), adolescent-parent relationships, and absenteeism status variables were important predictors of SEL scores at the student level. The variables of the relationship between students, teacher-student relationships, number of students/teachers, music class (active use), number of student clubs in the school, parental involvement, presence of school counselor, and disciplinary action rate were important predictors of SEL scores at the school level. Findings were thoroughly discussed in relation to the existing literature, and recommendations were made for future studies and applications.