Trusts have become a central part of the English education system, providing the core of school-to-school support, improvement and governance. This means that it is increasingly important for us to know what high quality looks like in a trust. In this paper we have reviewed the evidence from four countries: England, the US, the Netherlands and Sweden. The latter three countries were chosen as they have somewhat similar (though by no means identical) systems. This literature review draws on a search conducted using several evidence bases, websites of government agencies, and a general google search. We also drew on the references to other studies in those sources.