A study of the effects of an add-on early literacy intervention, consisting of a classroom- and home-based interactive reading program and the use of the Sound Foundations curriculum--a classroom-based phonemic awareness program, on outcomes in the areas of language, writing, linguistic awareness, and print concepts among Head Start children, based on data from 167 4-year-olds who attended classrooms in selected Head Start centers in Suffolk County, New York, during the 1992-1993 school year