Guided by a developmental-ecological framework and Head Start's two-generational approach, this study examined two dimensions of Head Start program quality, classroom quality and parent involvement and their unique and interactive contribution to children's vocabulary, literacy, and mathematics skills growth from the beginning of Head Start through the end of first grade. The study is a secondary data analysis of FACES 1997, a national descriptive study of Head Start children, families, and programs. The piecewise 3-level growth curve model suggested that Head Start children demonstrated positive academic growth trajectories over time, with vocabulary and literacy skills showing more rapid growth in Head Start years than in later grades. Younger children consistently showed more rapid growth than older children, especially during kindergarten and first grade. Head Start classroom quality and parent involvement uniquely and interactively predicted children's academic growth across time, but in rather complex ways. (Contains 4 tables and 1 figure.)