The long-term efficacy of scaled, real-world early-childhood programs

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For the Court

Scaled and real-world early-childhood efficacy is genuinely contested. The same literature contains a rigorous scaled RCT with null-to-negative long-term effects (Tennessee) and quasi-experimental evidence of lasting Head Start benefits — with fade-out common and persistence dependent on what follows the program.

What This Claim Does NOT Say

Does not claim scaled early-childhood programs are ineffective; some show lasting benefits (e.g., Head Start on adult outcomes; state programs paired with sustaining environments), and absence of uniform strong evidence is not evidence of absence.

Does not transfer model-program (Perry/Abecedarian) effect sizes or ROI to scaled programs or to IDEA Part C.

Does not establish that early test-score gains predict long-term benefit; such gains frequently converge as non-attenders catch up, while some non-test outcomes persist.

Does not resolve the active dispute in the literature; rigorous studies disagree, and effects depend heavily on program, population, and the subsequent environment.

Scope — Where It Holds

Evidence ranges from null-to-negative long-term effects in some rigorous scaled pre-K RCTs (Tennessee), through common fade-out of early test-score gains, to real persistence in other programs — especially where complementary "sustaining" investments follow. For early intervention under IDEA Part C specifically (services for infants and toddlers, roughly birth to age 3, with developmental delays or disabilities), the strongest evidence is observational/quasi-experimental and modest; no Part C randomized trial with model-program-scale long-term outcomes exists, because a randomized trial that withholds early-intervention services from eligible children is not feasible.

Sources & Verification

Seminal

Durkin, K., Lipsey, M. W., Farran, D. C., & Wiesen, S. E (2022). Effects of a statewide pre-kindergarten program on children's achievement and behavior through sixth grade. Developmental Psychology, 58(3), 470-484.
Experimental · N = 2,990
Scaled Tennessee Voluntary Pre-K RCT (N~2,990 randomized): null-to-negative effects on achievement and behavior through sixth grade. (Corrected 2022, supplemental coding.) [Consensus 2026-06 (3-pass); DOI-confirmed 2026-06-22]
Bearing on this claim: Tennessee scaled pre-K RCT: null-to-negative long-term — the wall against transfer.
doi.org/10.1037/dev0001301

Supporting

Stingone, J. A., McVeigh, K. H., & Lednyak, L (2026). Early Intervention Developmental Programming and Childhood Academic Outcomes. JAMA Network Open, 9(2), e2555890.

Limits & Counter-considerations

Evidence is mixed across strong designs; the one rigorous scaled pre-K RCT is negative long-term while observational and quasi-experimental studies are more favorable; effects depend heavily on program, population, and the subsequent environment; and for IDEA Part C no model-scale long-term RCT exists. Absence of uniform strong evidence is not evidence of absence — but it also cannot be read as confirmation of strong efficacy.

The long-term efficacy of scaled, real-world early-childhood programs — including state pre-K, Head Start, and IDEA Part C early intervention — is modest, heterogeneous, and contested, and does not reliably reproduce the magnitude of the model-program trials.