This study investigated the effect of full- and half-day kindergarten programmes on English language learners (ELL) and English-only-speaking children's literacy and mathematics performance in a large urban school district. Considerations were given to how the length of the school day, children's language status (ELL and non-ELL), and children's attendance patterns influenced achievement. Results reveal that all children in full-day kindergarten settings performed significantly better on spring literacy assessments and mathematics when compared to children in half-day settings. Non-ELL children performed significantly higher on spring literacy assessments than ELL children. Children who missed fewer than 10 days of kindergarten had significantly higher spring literacy and mathematics scores than children with more than 10 absences. Findings from this study have significant policy and practice implications related to the overall quality, availability, and the effect of kindergarten programming in the USA. (author abstract)