The rationale for the principles of effective school governance in England, as set out in government regulations, has never been made explicit. This article addresses that issue and develops and proposes such principles. We argue that effective school governance secures the legitimacy of schools as institutions. Such institutional legitimacy is achieved through the institutionalization processes in which the institutional primary task is central. Effective governance is therefore concerned with overseeing and ensuring the processes of institutionalization. We identify two general principles that relate to ensuring the school's legitimacy and ensuring that the school's institutionalization processes enable it to be a legitimate institution. We also distinguish six specific principles that relate to: the school's work on the institutional primary task, the resources required and deployed for work on the institutional primary task; the school's compliance with the rules and regulations that apply to the institution; the school's conformance to the norms expected of a school; the way the school operates on a day-to-day basis in relation to wider society's expectations; calling the headteacher or principal (HT/P) to account for the functioning of the school; and ensuring the HT/P's development. Our analysis is relevant to school governance in other countries.