Purpose: The purpose of this paper is to discuss how communication and cooperation in inter-organizational networks may bring about organizational learning. A case study of 13 inter-organizational school networks in Germany is carried out for this purpose. Design/methodology/approach: Results of a quantitative survey assessing the performance of the 13 networks are presented. A subsequent qualitative survey of two highly innovative networks takes into account the learning effects in school practice. The analysis is predicated on an activity theoretic view on learning and development. Findings: Two levels of consideration are distinguished: the learning platform where representatives of the schools regularly meet and the operational work at the schools. The perception of how the representatives in the network learned how the colleagues at the schools who are not directly involved learned and how the school as a whole learned is appreciated differently. Outcomes vary from "exchange of new ideas" to "implementation of school development." Research limitations/implications: The paper is based on empirical research carried out at one point in time. A longitudinal study of inter-organizational network performance could shed more light on the dynamic validity of the model. Practical implications: Understanding networks allow to appreciate their outcomes. The outcomes of this paper provide guides on how to design more effective learning networks. Originality/value: The conceptual model distinguishes between two network levels, its interrelated learning effects and the different stages of learning and development. Learning networks can be assessed due to the learning categories, and success factors can be identified. (Contains 6 figures.)