Table 5.

Cluster robust meta‐regression for random assignment for academic effect sizes.

Effect (n of effect sizes)	Hedges’ g	95% CI of g	df	p
Nonrandom assignment (72)a	0.19	0.07, 0.31	12.06	0.004
Random assignment (41)	0.28	−0.07, 0.63	5.76	0.095

Note: N of studies = 24, N of effect sizes = 113, assumed ρ = 0.8, I ² = 76.90. Cluster robust estimates with df < 4.00 should be interpreted with caution (Tanner‐Smith, Tipton, & Polanin, 2016). Positive effect sizes favor Montessori over traditional education.

Abbreviation: CI, confidence interval.

^a Reference category/intercept.