Head Start has focused on children living in poor families since the program’s inception in 1965. During the past decade the population of children eligible by income status increased: nationwide, 19% of children live in poor families and 41% live in low-income families (families with less income than twice the federal poverty threshold). Furthermore, poverty rates are highest among the young children of the U.S., with 44% of those under 6 now living in low-income families (National Center for Children in Poverty, Nov. 2009). Research over the past several decades established the importance of poverty to early development by examining the developmental mechanisms linked to both family income and child outcomes (i.e., Richter, 2010).
McCartney and Berry (2009) established the notion of "functionally equivalent environments." This conceptualization suggests that, in spite of large differences in the actual environmental opportunities afforded children via schooling, community and family and cultural values, the majority of children will somehow use what is available in order to do well. Children generally do well across most environments. There is agreement, however, that not all environments are "functionally equivalent" and capable of contributing to development "because below some threshold there are insufficient opportunities for adequate, species-normal development to occur" (Scarr, 1993, p. 1338). Poverty and very low—income status often qualify as being below minimal threshold for optimum development. Environmental differences may "explain individual differences in developmental outcomes, but the effect is non—linear" (McCartney & Berry, 2009). Within any single given environmental context, genetic differences express themselves as children develop and move toward maturity.
As seen in the conceptual model presented in Figure 1, family income affects child outcomes in at least three ways, two direct and one a mediator. Resources in the home, such as books and the Internet, have direct demonstrable effects, as do physical conditions, including safety and cleanliness of the home and immediate environment. A substantial body of research on parents demonstrates that parental mental health, which in turn affects parenting behavior, plays a mediating role in children’s behavior and adjustment. Parental mental health problems are more prevalent in poor and low income families, and hence family health and living conditions are importantly linked to children’s adjustment (McLeod and Shanahan, 1993).