This study evaluates the effectiveness of a large-scale training programme on pupil well-being. The research questions are (1) to what extent did the training programme have an impact at the level of schools, and (2) to what extent did the training programme have an impact at the level of pupils? Using a survey with teachers and school principals (n=899), a survey with primary school pupils (n=2,612), and semi-structured interviews and focus groups with the main stakeholders (n=14), it was concluded that, notwithstanding high participant satisfaction, no substantial effects on school practices or on pupil well-being could be observed. Insufficient training time and the absence of post-training school counselling were key factors in the lack of success.