Recent educational goals have expanded to include socio-emotional development and subjective well-being (SWB) at school, alongside academic performance. However, just a few studies have focused on the longitudinal determinants of school SWB across different educational stages. Therefore, socioemotional (ability self-concept, social integration, classroom climate, feeling accepted by teachers) and sociodemographic (gender, socioeconomic status and migration background) determinants of school satisfaction and school mood were investigated among both elementary and secondary school students. Specifically, the data of N = 416 elementary (n = 205 girls, age: M = 8.19; SD = 1.04) from Grade 2 to 4, and N = 306 secondary school students (n = 172 girls, age: M = 11.82; SD = 0.93) from Grade 5 to 7 were analysed at two time points. Results of structural equation models showed that ability self-concept, feeling accepted by teachers and gender were significant predictors of changes in school SWB, with differences according to the educational stages. The findings underscore the importance of students' self-concept and teacher-student relationships in maintaining the educational goal of promoting high levels of SWB.