Early Childhood Longitudinal StudyIncludes three longitudinal studies that examine child development, school readiness, and early school experiences. The birth cohort of the ECLS-B is a sample of children born in 2001 and followed from birth through kindergarten entry. The kindergarten class of 1998-99 cohort is a sample of children followed from kindergarten through the eighth grade. The kindergarten class of 2010-11 cohort is following a sample of children from kindergarten through the fifth grade.