This paper (1) reviews the literature on the relationship between entrance age into kindergarten and academic achievement and (2) reports a study of the effect of entrance age on school success. Some experts say that age alone is the best indicator of success. Others say that chronological age, mental age, intelligence quotient, readiness, emotional and social adjustment, or combinations of these factors are the indicators of success. A few experts say that age is not an indicator of success at all because each child can succeed if the school program meets individual needs. To explore these issues, an investigation compared the academic achievement at the third grade level of 20 early and 20 late entry kindergarten children. A statistically significant difference in achievement was found, with the late entry students scoring significantly higher on the Iowa Test of Basic Skills than did those who entered kindergarten early. In addition, findings revealed that 61 percent of the students who were retained in elementary or placed in modified primary classes were within the early entry group at the time of admission to kindergarten. (Author/RH)