This study examined the relations of age, preschool experience, and gender with children's school readiness levels at kindergarten entry. The sample included 5,512 children of predominantly Hispanic heritage and from families experiencing low socioeconomic circumstances. A series of between-subjects ANOVAs indicated that age (Eta[squared] .019 to .043), preschool experience (Eta[squared] .104 to .204), and gender (Eta[squared] .015 to .022) were significantly related to children's school readiness as measured by the Kindergarten Student Entrance Profile (KSEP). Logistic regression examined the unique contribution of these variables to predict students' academic achievement at the end of Grade 2 with a subsample of 980 students. The strongest achievement predictor was school readiness -- the odds of students rated in the top 25% on the KSEP having proficient or advanced scores on the English Language Arts portion of the California Standards Test at the end of Grade 2 were 4.51 greater than the odds of students rated in the bottom 75% on the KSEP having proficient or advanced scores. Similar results were found for students' achievement in mathematics. The key findings of this study showed that formal preschool experiences play an important role in preparing children of Hispanic descent and who live in households experiencing low income for kindergarten entry. However, children's readiness at entry into kindergarten was more strongly related to later academic achievement than age at kindergarten entry and preschool experience. (author abstract)