There are many possible mechanisms through which school collaborations may bring about change in educational and/or social outcomes. Schools collaborating to share professional expertise may improve teaching practice and in turn lead to better educational outcomes for pupils. Schools collaborating to share resources, be they equipment, staff or learning resources may also improve the standards of teaching and educational outcomes. This systematic review will seek to answer the following key questions: (1) do inter-school collaborations improve educational and social outcomes for students; (2) do different types of inter-school collaboration lead to different effects on educational and social outcomes for students; (3) for each type of inter-school collaboration, is it possible to identify whether there are key characteristics that optimise their effectiveness on educational and social outcomes for students; and (4) do inter-school collaborations have differing effects for students depending on their initial levels of attaining, their socio-economic backgrounds, their gender, their ethnicity and/or their minority status. If so, do these differential effects vary in relation to differing types of inter-school collaboration?