This report discusses the practicalities of how a schools market should operate by comparing international case studies. There is currently much debate over school choice as an element of educational reform, with the arguments for developing a market between state-funded schools revolving around the ideas of choice and competition. The goal in this paper is to refigure the debate towards evidence rather than theory, and to learn the lessons of existing school reforms in England (the academies programme), Sweden (free schools) and the US (charter schools). The report assesses the success of reforms in all three countries against seven criteria which a schools market should meet in order to find the right balance between promoting innovation and choice while maintaining accountability and quality control. None of the countries studied have achieved this balance yet, though in each case the introduction of new providers to the system has brought benefits, but all of the seven criteria are met by at least one country. By combining the best aspects of each system, the authors argue, it is possible to develop a set of school choice reforms that will increase diversity and performance while protecting against market failure.