Lifetime Effects: The HighScope Perry Preschool Study Through Age 40 - Schweinhart, L. J.; Montie, J.; Xiang, Z.; Barnett, W. S.; Belfield, C. R.; Nores, M. (2005)
rct; evidence grade C

Multiple Inference and Gender Differences in the Effects of Early Intervention: A Reevaluation of the Abecedarian, Perry Preschool, and Early Training Projects - Anderson, M. L. (2008)
critique; evidence grade B

The Rate of Return to the HighScope Perry Preschool Program - Heckman, J. J.; Moon, S. H.; Pinto, R.; Savelyev, P. A.; Yavitz, A. Q. (2010)
quasi-experiment; evidence grade D

The Perry Preschoolers at Late Midlife: A Study in Design-Specific Inference - Heckman, J. J.; Karapakula, G. (2019)
replication; evidence grade B

Adult Outcomes as a Function of an Early Childhood Educational Program: An Abecedarian Project Follow-Up - Campbell, F. A.; Pungello, E. P.; Miller-Johnson, S.; Burchinal, M.; et al. (2012)
rct; evidence grade B

Quantifying the Life-Cycle Benefits of an Influential Early-Childhood Program - García, J. L.; Heckman, J. J.; Ermini Leaf, D.; Prados, M. J. (2020)
quasi-experiment; evidence grade D

Family Environment and the Malleability of Cognitive Ability: A Swedish National Home-Reared and Adopted-Away Cosibling Control Study - Kendler, K. S.; Turkheimer, E.; Ohlsson, H.; Sundquist, J.; Sundquist, K. (2015)
twin-adoption; evidence grade B

The Environment in Raising Early Intelligence: A Meta-Analysis of the Fadeout Effect - Protzko, J. (2015)
meta-analysis; evidence grade B