One of the conundrums of free primary education (FPE) policy in several countries in Sub-Saharan Africa is the ‘mushrooming’ of fee-paying private schools. Several researchers have become interested in studying this phenomenon and have raised the question—does free primary education meet the needs of the poor? Emerging voices among this group of researchers suggest that the impact of FPE, particularly in meeting the educational needs of the poor may be over-stated in situations where the poor still utilize what is referred to as ‘private schools for the poor’. The concerns expressed by those voicing this point of view point to the question of why the poor choose fee-paying [low quality] private schools when there is, presumably a free state school? To respond to this question and to contribute to this debate, this paper adopts the excess demand and differentiated demand frameworks to analyse how slum (poor) and non-slum (non-poor) parents utilize education in Nairobi, Kenya following the implementation of free primary education policy in 2003. We conclude that the answer to the ‘mushrooming’ of private schools for the poor is ‘excess demand’. As to whether free primary education meets the needs of the poor, we argue that where supply does not match demand excess demand is likely to arise in the initial stages. We recommend that what is required is greater and possibly differentiated and better targeted investment in education whereby unequals are treated unequally in order for the Kenyan government not to under-invest in the education of the poor.