Concerns related to school are consistently ranked as among the greatest stressors in the lives of adolescents. Research from varying contexts report rising rates of school-related stress among students, but we currently lack knowledge on what drives these trends. The aim of this study is to investigate the predictors of temporal trends in school-related stress in Swedish students between 2003 and 2020. To this end, repeated surveys of 9807 Swedish students aged 16 years are analysed using Blinder-Oaxaca decomposition techniques. The results show that the rise in school-related stress was primarily due to growing schoolwork difficulties and social exclusion among students, indicating possibly adverse consequences of a large-scale educational reform as well as of the COVID-19 pandemic. In addition, rising academic aspirations contributed to the increase, in line with arguments concerning the increasing weight attached to educational success among adolescents in the 'schooled society'.