The mantra ‘schooling ain’t learning’ (Pritchett, 2013) captures a view that children in many developing countries learn little in school. This study critically assesses whether such normative claims about school productivity hold-up to scrutiny. The first part sets out the challenges of evaluating the contribution of schools to achievement gains and shows existing evidence for low income countries is scant and fragile. The second part provides an original analysis of data from East Africa, covering over 700,000 children. Results from a sibling difference model reveal that the absolute contribution of schools to achievement gains is inadequate in light of national curriculum expectations. However, a new metric of relative school productivity, which evaluates achievement gains due to schooling against background rates of cognitive development associated with ageing, suggests the relative magnitude of gains due to schooling are more comparable to those in advanced countries. The gap between absolute and relative metrics of school productivity suggests that ‘learning ain’t just about schooling’. Rather, learning potential is conditioned by a wide range of background factors, including the early childhood environment.