This paper articulates the first 'general theory' of prison education, offering a new insight into the relevance of desistance theory and understanding of prison sociology to the lives of men engaged in education whilst in prison. Using a realist review method (Pawson, 2002b; Wong, 2013a) we develop a rough, initial general theory of prison education articulated in the form of three context-mechanism-outcome configurations (CMO). We then 'test' these CMOs by assessing the current evidence base through a systematic review of literature. This paper articulates three inter-related CMOs that we ground in prison sociology and desistance literature: 'hook', 'safe space' and 'qualifications'. 'Hook' refers to engaging in prison education as a 'hook for change' and its impact on personal identity. 'Safe space' refers to the space an educational class can provide and its relevance to social identity. 'Qualifications' refers to the relevance of skills and qualifications gains. The literature review takes a targeted view of relevant fields to identify the most relevant evidence base for (or against) the three CMOs under scrutiny. We identify a stronger evidence base to support the 'safe space' and 'hook' CMOs than for the 'qualifications' CMO. However, the research is limited by a narrow focus on literature. We outline the next steps for future researchers to build on this work.