5. Conclusions
In conclusion, contrary to our expectations, the results of this follow-up study of a single-tier (DSP) and a multi-tier (DSP + MHST) intervention on psychological and academic adjustment outcomes indicated no significant effects compared with the control group. We underscore the importance of viewing these results in the context of the abovementioned limitations. Moreover, the school is a complex system as a setting and subject of research. Future similar studies should be attentive to the potential challenges of implementing RCTs in the school setting. Furthermore, the long-term effects of school interventions on constructs, like those examined in this study, could be difficult to observe or promote owing to the complexity of the phenomena. Although a range of school factors can influence students’ psychological wellbeing and academic functioning, there is still a range of factors outside the school arena influencing psychological distress, loneliness, life satisfaction, absence, grades, and ability to stay in school that the school setting cannot directly address. Future research could consider addressing a wider array of life domains of adolescents that are relevant for school thriving to better understand how school interventions can work effectively.