Increasingly, innovative collaboration between industry and schools is being exploited as a way of improving the quality and relevance of education. Even though these innovations appear to have substantial benefits, often the impact proves to fade away after their implementation. A better understanding of how to sustain complex innovations seems important. Unfortunately, only a limited amount of research investigates the "inside" of complex innovations. This article reports on a three-year, large-scale industry-school programme in the Dutch Leisure sector. The research, from start to finish, adopted a qualitative case study methodology with a mixed-methods approach, drawing upon social capital theory as lens to understand the dynamics of processes and effect on outcomes. Findings indicate that the social capital theory helps to unravel crucial factors of processes and outcomes. The researched innovation process depended not so much on formal project plans and objectives but largely built on the quality of social relationships at all levels. Sustaining this social capital proved crucial, while managing according to a planned change strategy appeared to be counterproductive. The outcomes show to be twofold, in terms of new knowledge and products for the organisations and of sustainable benefits for the professionals, in terms of new abilities.