Having recently shared some of the most promising recent RCT findings, I now share one of the most disconcerting: The long-term results of the Tennessee voluntary pre-k study. Quick take: High-quality RCT finds adverse effects on student achievement & behavior in 6th-grade follow-up.


  • Tennessee’s voluntary pre-k (VPK) program is a statewide program for 4-year-old children from low-income families. In 2009-10, when the treatment group received VPK, the program met 9 of 10 quality benchmarks of the respected National Institute for Early Education Research (link, p. 133).

Study Design:

  • The study randomly assigned 3,131 children, via lottery, to VPK vs control. The authors recently published results of a 6th-grade follow-up. Based on careful review, I believe this was a high-quality RCT (e.g., with low attrition & good baseline equivalence)


  • Statistically significant adverse effects on English language arts, math, & science on the state test. Effect sizes were about -0.15, meaning VPK would've moved the average control group child from the 50th to 44th percentile had he or she been assigned to the VPK group.

  • Also: modest adverse effects on % of special ed placements (12% VPK vs 8% control) & disciplinary events in grades K-6 (effect size 0.09) - both statistically significant.


  • It's unclear what accounts for VPK's adverse effects. Study author Dale Farran offers some ideas.

  • Both this study & the national Head Start RCT found positive effects at end of pre-k that dissipated as kids entered grade school. But in VPK (unlike Head Start) the impacts turned negative. Here's the new VPK paper with grade 6 findings.

  • The findings underscore why it's essential for government funding of pre-k to incorporate evidence-based criteria aimed at ensuring effectiveness - e.g., RCTs to identify truly effective practices (curricula, teacher training, etc.), & funding to implement these practices - as discussed here.

We use cookies to improve your experience and to help us understand how you use our site. Please refer to our cookie notice and privacy statement for more information regarding cookies and other third-party tracking that may be enabled.

Intuit Mailchimp logo