ABSTRACT
As discussed above, most evaluations of the Head Start program have focused on measures of IQ and other measures of cognitive achievement. A ‘meta-analysis’46 of 72 studies conducted by the US Department of Health and Human Services (McKey et al., 1985)47 is summarized in Figure 8. The figure shows the weighted average effect of participation in Head Start from the subset of studies that used an experimental
treatment and control design.48 The scale was chosen so that gains of .25 or greater can be thought of as educationally meaningful in the sense that they are accompanied by noticeable improvement in classroom performance. Hence the figure shows large gains upon entry to regular school that dissipate rapidly. McKey et al. (1985) note that the sources of these gains are not well understood. Studies that have examined the effects of different types of curricula, class size, length of the school day, racial and ethnic composition of the class, and type of program administration have produced weak or conflicting results.
