In recent years, biographical interviews with former pupils have become important sources for boarding school history. This raises the question as to whether these retrospective sources can be combined with contemporary written material and how to go about that. This paper argues for a triangulation of written with oral sources and the related methods of historical biography research and reconstructive social research. The combination of data and methods turns boarding school history into an interdisciplinary project that poses new challenges for research. At the same time, it also offers a way to a deeper understanding of boarding school history and its long-term effects.