For "Total number of classes failed", this is the number of classes failed by per member of sample group (asked at age 23). Results are from a study of different curriculum models impact on disadvantaged children in New Jersey. The sample groups are randomly selected and have comparable socio-economic backgrounds and other background characteristics. “ Child Centred (constructivist)" is a High/Scope curriculum model, "Child Centred (social)" is a Nursery School programme with a focus on social skills.