How to best utilize curriculum time has long been a question for England’s schools, which are free to vary time between subjects or to extend the school day/week. This question has now risen to national prominence as policymakers consider ways to help support students catch up lost learning after the COVID-19 pandemic. This article explores the relationship between instruction time on General Certificate of Secondary Education (GCSE) attainment and value-added scores for 2,815 English secondary schools using panel data from the 2010–14 School Workforce Census. Robust estimates suggest that instruction time has a small effect on attainment in each of English, mathematics, science and humanities. Based on sub-group analysis, effects sizes are also estimated for students with varying prior achievement and for those in receipt of free school meals. These too appear small, suggesting, vis-à-vis instructional time, sometimes less might be more.