This paper estimates models of the evolution of cognitive and noncognitive skills and explores the role of family environments in shaping these skills at different stages of the life cycle of the child. Central to this analysis is identification of the technology of skill formation. We estimate a dynamic factor model to solve the problem of endogeneity of inputs and multiplicity of inputs relative to instruments. We identify the scale of the factors by estimating their effects on adult outcomes. In this fashion we avoid reliance on test scores and changes in test scores that have no natural metric. Parental investments are generally more effective in raising noncognitive skills. Noncognitive skills promote the formation of cognitive skills but, in most specifications of our model, cognitive skills do not promote the formation of noncognitive skills. Parental inputs have different effects at different stages of the child's life cycle with cognitive skills affected more at early ages and noncognitive skills affected more at later ages. (Contains 17 tables and 39 footnotes.)