In October 2015 the Department for Education (DfE) permitted a grammar school in Tonbridge, Kent, to open up an annexe in Sevenoaks, 10 miles away. Amidst claims that the annexe was essentially a new grammar school, the decision reignited an old debate about the value of academically-selective "grammar" schools in England. The intensity of feeling is perhaps surprising given that all but a small number of grammar schools have long been replaced by mixed-ability "comprehensive" schools. Yet, the matter taps into longstanding debates around standards, social mobility, opportunity and accessibility. A resurgence of these discussions is now playing out in a changed political and educational landscape characterised by school autonomy, diversity of provision and school choice. This article describes the key shifts that have taken place in English school organisation and policy thinking since the establishment of the tripartite system and the recent emergence of new roles and opportunities for grammar schools. This is followed by a review of the evidence on the effectiveness and wider social impact of selective education. The article concludes by reframing the grammar school debate in light of the evidence and the current system, arguing that issues around system performance and social segregation need to be examined more broadly and that the most fruitful debates to be had are around admissions and accountability mechanisms rather than structures and school types.