Increasing extreme heat events in the tropics are creating dangerous environments in schools. There are limited data, however, on the extent of extreme heat in such classrooms and effective heat-mitigation strategies. This study presents the first long-term analysis of classroom temperatures in Ghanaian schools, measuring conditions in 16 classrooms in Accra over 389 days. It highlights the conditions experienced by schoolchildren and examines how roof type influences classroom temperatures. Children in metal-roofed classrooms were exposed to extremely high temperatures of up to 39.8°C, exceeding outdoor temperatures by up to 5.9°C, and being overheated for 72.5% of occupied hours, posing risks to children’s health and learning. Concrete-roofed classrooms were significantly cooler than those with metal roofs (by up to 5.8°C) and were on average 1.2°C cooler than the outdoor temperature, thus exposing children to fewer hours of uncomfortably hot temperatures. Adding a plywood ceiling under a metal roof halved overheating-hours, compared with a bare metal roof. These findings highlight the need for heat-resistant design principles when constructing or retrofitting schools to create safer, healthier classroom environments that are more conducive to supporting learning and the health of children in tropical climates. Policy relevance The findings of the first long-term monitoring of temperatures in 16 school classrooms in tropical Africa allow for evidence-based policymaking. This research highlights the urgent need to build and retrofit schools so they are heat-resistant to improve children’s learning ability and health. Using this new evidence of extreme heat in classrooms in Ghana, policymakers should revise the School Establishment and Inspection Policy and the Ghana Building Code to include climate-resilient design principles, prioritising heat-resistant roofing materials. This model can be replicated across tropical Africa to create heat-resistant schools and help address United Nations’ Sustainable Development Goal (SDG) 4 to ensure quality education in a changing climate.