A study examined whether preschool attendance has a positive effect on reading achievement of third graders. Subjects were 40 students attending third grade at the Benjamin Wright Raymond Public School (100% minority students), located in a mostly low socioeconomic neighborhood in the Chicago, Illinois area. Half of the subjects had attended preschool. Data on students' reading scores and achievement levels were gathered from students' 1994 Iowa Tests of Basic Skills. Results indicated that students at the third-grade level who attended preschool achieved higher reading scores than children who did not attend preschool. Findings suggest that reading achievement gains made by preschoolers are retained through the third grade. (Contains 14 references and one table of data.) (RS)