In 1982, the Maryland State Department of Education initiated a longitudinal study of its Extended Elementary Education prekindergarten program. The study was designed to examine the school performances of program participants and members of a comparable nonpreschool group. At the time of this analysis, study participants were 16 years of age. Major questions addressed by the study were: (1) What effect does prekindergarten have on participants' school behavior in comparison to school behavior of members of the nonpreschool group? (2) Does prekindergarten participation improve economically disadvantaged children's performance to the extent that they achieve at a level comparable to that of children from a variety of socioeconomic backgrounds? (3) If prekindergarten leads to higher achievement, are the differential effects sustained over time? and (4) Does the achievement gap between the prekindergarten and nonpreschool groups widen as they progress through school? In this phase of the study, the effects of prekindergarten were traced from kindergarten though ninth grade. The findings show that prekindergarten participation sets in motion a linear path of effects that leads to improved academic performance through the beginning of high school. Citations number 32. (RH)