A National Randomized Controlled Trial of the Impact of Public Montessori Preschool

Published in PNAS, October 20, 2025.

Though a strong body of evidence tells us about the effectiveness of preschool programs in general, there is less evidence about which models in particular are most effective. The Montessori preschool model is a popular choice for many families, and it has expanded substantially into public schools in the U.S. over the past two decades, but until now, there has never been a rigorous, large-scale study of its effectiveness compared with other preschool models.

In this study, conducted in partnership with the University of Virginia and School Readiness Consulting, we take advantage of existing admissions lotteries to public Montessori programs for three- to six-year-olds, to understand the impact of Montessori through a rigorous randomized controlled trial framework.

Although there were no notable impacts at the end of the children's three- or four-year-old years (PK3 or PK4), at the end of kindergarten, Montessori students had significantly higher reading, short-term memory, theory of mind, and executive function scores, compared to students who participated in a more traditional preschool program or had another early childhood experience.

Further, a cost analysis found that three years of a public Montessori program from PK3 through kindergarten costs less per child than traditional programs, largely due to the Montessori program design having higher child-to-teacher ratios in PK3 and PK4.

Future research will examine the impact of Montessori preschool on students' elementary school test scores.