National Center for Education Statistics Early Childhood Longitudinal Studey"The Early Childhood Longitudinal Study (ECLS) program includes 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."