School belonging, defined as extent to which students feel accepted, supported and emotionally engaged in the school, is an important determinant of student's academic and psychological adjustment. School belonging is affected not only by individual but also by peers, families and teachers; broader organisational school system and social values, norms and policies. The current study investigated personal (social competence, scholastic competence, global self-worth) and contextual factors (family factors, classroom factors, classroom environment factors) that contribute to school belonging in secondary and high school students. The research sample consisted of 148 secondary (67 boys, 81 girls, Mage = 13.94(0.70)) and 177 high school students (69 boys, 108 girls, Mage = 15.63(1.15)). Results indicated that 11 personal and contextual factors collectively explain 42% of the variability in school belonging among secondary school students and 58.4% of the variability among high school students. The majority of the variance in school belongingness in secondary schools was explained by student's personal factors (17.2%), social competence being significant predictors, and classroom factors (15.8%), classmates support being significant predictor, followed by family factors (8.2%), parental support being significant predictor. In high school students, the majority of the school belonging variance was explained by personal factors (54%), such as social competence and global self-worth, followed by classroom factors (3.2%), such as classmates support. Classroom environment did not show as significant predictors of belonging in both secondary and high school students. In secondary school students the classmates support was the most robust contributor to school belonging, in contrary, among high school students the social competence was the strongest predictor. Our results provide information about factors that should be emphasized through interventions, system changes or policy reforms to best support students of secondary and high schools.