Belonging is an essential aspect of psychological functioning. Schools offer unique opportunities to improve belonging for school-aged children. Research on school belonging, however, has been fragmented and diluted by inconsistency in the use of terminology. To resolve some of these inconsistencies, the current study uses meta-analysis of individual and social level factors that influence school belonging. These findings aim to provide guidance on the factors schools should emphasise to best support students. First, a systematic review identified 10 themes that influence school belonging at the student level during adolescence in educational settings (academic motivation, emotional stability, personal characteristics, parent support, peer support, teacher support, gender, race and ethnicity, extracurricular activities and environmental/school safety). Second, the average association between each of these themes and school belonging was meta-analytically examined across 51 studies (N = 67,378). Teacher support and positive personal characteristics were the strongest predictors of school belonging. Results varied by geographic location, with effects generally stronger in rural than in urban locations. The findings may be useful in improving perceptions of school belonging for secondary students through the design of policy, pedagogy and teacher training, by encouraging school leaders and educators to build qualities within the students and change school systems and processes.