Early Childhood Interventions: Proven Results, Future Promise / RAND, 2006

PDF - http://www.rand.org/pubs/monographs/2005/RAND_MG341.pdf
"Considers the potential consequences of not investing additional resources in children�s lives, the range of early intervention programs, the demonstrated benefits of interventions having high-quality evaluations, the features associated with successful programs, and the returns to society associated with investing early in the lives of disadvantaged children. The findings indicate the existence of a body of sound research that can guide resource allocation decisions."