Population ageing has triggered concerns about the sustainability of public systems of education. The empirical evidence is still inconclusive, whereas some theoretical results present a somewhat optimistic view (Gradstein and Kaganovich, 2004; Levy, 2005). The present note re-examines the political economy of public education in an ageing society, using the classical median voter model. The normative analysis shows that elderly households introduce distortions that render political outcomes inefficient except in rare circumstances. It is then explained that the interplay among the political and financial consequences of ageing gives rise to a non-linear, and possibly non-monotonic (inverted-U shaped) relationship between spending per pupil and the share of childless households in the population. Income inequality is shown to play a crucial role of in the process, revealing that ageing has a stronger tendency towards underprovision in economies with high inequality. The implications for the empirical literature are discussed.