Science curricula at the elementary school level frequently emphasize the “concrete,” with a focus on the processes of observation, ordering, and categorization of the directly perceivable. Within this approach, abstract ideas and the planning of investigations and analysis of their results are in large part postponed until higher grades. This practice stems from purported developmental constraints on children’s thinking. This article analyzes these constraints in light of the writings of Piaget, to whom they are frequently attributed, and contemporary developmental theory and research. Neither the Piagetian nor the non-Piagetian research supports the validity of these developmental assumptions. The article also identifies several intrinsic problematic aspects of this approach to children’s science, including the failure to appreciate the challenge of adequate scientific description, the liabilities of decontextualization, and the epistemological messages it conveys to children. Both Piagetian and non-Piagetian literatures support the feasibility of children’s science curricula in which the processes previously approached as ends become tools in contextualized and authentic scientific inquiry.