Objectives: This study sought to evaluate the efficacy of a brief version of the Happy Classrooms Programme in psychological well-being, school aggression, and positive classroom climate. Likewise, this study also aimed to identify which intervention effects could be attributed to the development of mindfulness. Finally, the last target of this study was to evaluate the implementation fidelity and the acceptability of the programme.Methods: Multiple linear regression and longitudinal mediation analyses were performed with a sample of 524 students (49.8% boys and 50.2% girls) with a mean age of 13.6 years.Results: Results provided evidence of the efficacy of the intervention in the majority of variables. For

In recent years, there has been significant growth in positive education programs and experiences around the world. From an international perspective, there is considerable variety in practices in this field. It is encouraging to note that positive psychology is entering the classrooms and becoming an important movement for educators in many countries. But at the same time, it is critical to reflect on the evolution of this movement and assess whether its implementation is having the desired effects. Current practices are varied and not all of them meet necessary quality standards. Furthermore, it is necessary to analyse the enabling and hindering conditions that arise from practice in educational settings, so as to better understand what is working well and what needs to be improved. This chapter discusses these issues, suggests proposals for implementation for practitioners, and highlights the necessity for positive education to be available for all educational settings and contexts, regardless of characteristics or financial resources.