This study investigated the effectiveness of the Full-Day Early Learning Kindergarten (FDELK) programme, which integrates play-based learning and team teaching, in promoting 32,027 kindergarteners' self-regulation (SR), literacy, and numeracy outcomes. Outcome measures derived from teacher reports of students' school readiness in the Early Development Instrument were analysed in separate hierarchical regression analyses that controlled for individual and school-level characteristics. Results revealed essentially no benefit for students participating in the FDELK programme when compared to peers in Half-Day Kindergarten (HDK) or Alternate-Day Kindergarten programmes. Being older, female, and in higher socio-economic status schools with a history of higher achievement predicted more positive SR, literacy, and numeracy outcomes. Findings suggest the FDELK programme requires improvement. Play-based learning programmes, such as the FDELK, might be enhanced by incorporating evidence-based guidelines and goals for play, reducing class sizes to more effectively scaffold learning, and revising curriculum expectations to include a greater focus on SR, literacy, and numeracy skills.