The performance of South Africa's educational system in national and international tests indicates that a large proportion of its public schools are underperforming. Ineffective leadership has been put forward as one reason. This paper analyses a leadership development programme, Partners for Possibility (PfP), which seeks to strengthen leadership in underperforming schools. PfP employs a one-year, cross-sector social partnership that pairs school principals with business leaders. Literature on leadership development attests to the problem of learning transfer. Interviews were conducted with 9 PfP principal business leader dyads and 4 PfP unpaired participants. The research also included observations of PfP meetings and analysis of PfP reports. Although PfP's partnerships were found to support the school principals' learning, the cost of the programme limits its scalability. PfP's group learning component was also found to sometimes divert partnerships from transformational to transactional forms. This study contributes to the understanding of learning transfer within social partnerships. It also highlights a limitation of programmes such as PfP, which aim at school improvement, but are not focused on instructional practice. The article explores ways in which partnership programmes could be strengthened.