This evaluation of the long-term effect of attending an all-day kindergarten program on academic achievement found that students in grade 1 who had attended the all-day program had a significant advantage over students who had attended a traditional half-day program. A 3-year longitudinal assessment was made for two cohorts of students, one that started grade 1 in 1987 and one that started grade 1 in 1988. Elementary school achievement test scores of students who had attended the full-day program were compared with the scores of students who had attended a half-day program. A previous study evaluated the effects of attending the full-day program on the 1987 cohort for the first 2 years of elementary school. Both studies found a significant advantage of the full-day program over the half-day program. However, the achievement difference between the groups lost significance after the first year of elementary school for the 1987 cohort. The difference remained significant for the 1988 cohort in the second year, but further study is needed to determine whether this difference remains prominent. Statistical data are presented in 14 tables. A list of five references is appended. (FMW)