Abstract
Background/Objectives: In light of the concerning research data on students' mental health, it is essential to provide high-quality programs that support children and young people in strengthening their psychological well-being. To address this need, the three-year Erasmus+ KA3 international project PROMEHS: Promoting Mental Health at Schools was developed. The project involved universities and education policy representatives from seven European countries, Italy (project leader), Greece, Croatia, Latvia, Malta, Portugal, and Romania. Its core activities included the development of the PROMEHS curriculum, grounded in three key components: social and emotional learning, resilience, and the prevention of behavioral problems, alongside a rigorous evaluation of its implementation. The main research aim was to test the effect of PROMEHS on students' and teachers' mental health. Methods: In Croatia, the curriculum was introduced following the training of teachers (N = 76). It was implemented in kindergartens, and primary and secondary schools (N = 32), involving a total of 790 children. Using a quasi-experimental design, data were collected at two measurement points in both experimental and control groups by teachers, parents, and students. Results: The findings revealed significant improvements in children's social and emotional competencies and resilience, accompanied by reductions in behavioural difficulties. These effects were most evident in teachers' assessments, compared to parents' ratings and student self-reports. Furthermore, teachers reported a significantly higher level of psychological well-being following implementation. Conclusions: Bearing in mind some study limitations, it can be concluded that this study provides evidence of the positive effects of PROMEHS in Croatian educational settings. Building on these outcomes and PROMEHS as an evidence-based program, a micro-qualification education was created to ensure the sustainability and systematic integration of the PROMEHS curriculum into Croatian kindergartens and schools.