Promoting student well-being in schools: Intervention effects and the role of student-student relationships and intrinsic motivation.

Background Student well-being is a core educational goal and a foundation for successful learning, yet it tends to decline during secondary school. Many school-based interventions show promising but inconsistent effects on student well-being. Also, the role of individual and classroom factors in shaping effects remains unclear.Aims We examined (1) changes in student well-being across a 10-week intervention programme comparing three sets of well-being strategies with a placebo control and (2) whether baseline student-student relationships and intrinsic motivation to participate moderated student well-being trajectories.Sample A total of 685 Grade 8 students (51% male; t1: Mage = 14 years, SD = 0.6) from 44 classes across 17 schools in Switzerland participated in our study.Methods Classes were randomly assigned to three experimental conditions or a placebo control. Student-reported well-being (three positive, three negative dimensions), student-student relationships and intrinsic motivation were assessed at baseline, mid-intervention, post-intervention and an additional 8-month follow-up. We estimated repeated-measures linear mixed-effects models. Given a non-significant main condition effect, moderator analyses contrasted high versus low baseline relationships and motivation.Results Across student well-being dimensions, significant time effects were observed, but few condition or interaction effects were found. Student well-being declined over time, irrespective of condition. Students with stronger baseline student-student relationships and/or higher baseline intrinsic motivation reported higher scores on positive well-being dimensions.Conclusions Individual resources-student-student relationships and intrinsic motivation-were more strongly related to student well-being than participation in a specific condition. Interventions may need to deliberately strengthen such resources and tailor their components to student and classroom contexts.