With the Obama administration proposing to build new preschool funding right into the Elementary and Secondary Education Act going forward, the expansion of government preschool continues apace. Even if Congress resists, the movement has strong momentum at the state and local levels.
So is universal public preschool inevitable at this point? The evidence for preschool’s effectiveness is so weak that I once thought cooler heads would prevail. As I wrote for NR last February: “It’s not too late for policymakers to pull back, quiet the true believers, and take a hard look at the data.”
But the preschool push is strikingly similar to an older movement with little evidence behind it: full-day kindergarten.
A working paper published last fall by the University of Virginia’s Chloe Gibbs investigated the impact of full-day versus part-day kindergarten using a random-assignment lottery. More interesting to me than the study, however, is the literature review. Until this paper, there had apparently been no high-quality experimental evidence supporting full-day kindergarten. There were only observational studies, inferences from related work, and non-experimental matching exercises that could not eliminate selection bias. These below-gold-standard studies tended to show inconsistent and ephemeral effects. Sound familiar?
“Research on the benefits of full-day kindergarten,” Gibbs summarizes, “. . . is mixed and lacking in rigorous approaches to estimating program impact.” Nevertheless, full-day kindergarten grew rapidly over the last two decades. Half-day kindergarten was the norm up through the early 1990s, but now 75 percent of public-school kindergarteners attend for a full day.
Whatever the cause of this rapid expansion, it certainly wasn’t the overwhelming weight of scholarly evidence.
Consistent with the preschool literature, the Gibbs study does show, at the end of the year, verbal ability gains for full-day compared with half-day kindergarteners. The real test, however, is whether the gains last over the years — preschool gains generally do not — so hopefully there will be follow-ups.
In the world of politics, though, new results are unlikely to matter. The experiences of both kindergarten and now preschool show that politicians need only the barest hand-waving hints of positive impacts — not solid evidence — to justify extending the state further into the spheres of society that were once off-limits.