A National RCT of the Impact of Public Montessori Schools on Early Childhood Outcomes
Saved in:
| Title: | A National RCT of the Impact of Public Montessori Schools on Early Childhood Outcomes |
|---|---|
| Language: | English |
| Authors: | Angeline S. Lillard, David Loeb, Karen Manship, Emily Davis Daggett, Juliette Berg, Society for Research on Educational Effectiveness (SREE) |
| Source: | Society for Research on Educational Effectiveness. 2025. |
| Availability: | Society for Research on Educational Effectiveness. 2040 Sheridan Road, Evanston, IL 60208. Tel: 202-495-0920; e-mail: contact@sree.org; Web site: https://www.sree.org/ |
| Peer Reviewed: | Y |
| Publication Date: | 2025 |
| Document Type: | Reports - Research |
| Education Level: | Early Childhood Education Preschool Education Elementary Education Kindergarten Primary Education |
| Descriptors: | Public Schools, Montessori Schools, Preschools, Outcomes of Education, School Effectiveness, Kindergarten, Achievement Tests, Preschool Children, Cognitive Tests, Literacy, Memory, Executive Function, Theory of Mind, Mathematics |
| Assessment and Survey Identifiers: | Woodcock Johnson Tests of Achievement, Digit Span Test |
| Abstract: | Background/Context: Montessori preschool instruction in public schools is now widespread throughout the United States, with over 560 public Montessori schools, roughly a quarter of which start at age 3 (National Center for Montessori in the Public Sector, n.d.). Despite the widespread popularity of the model, until now there has never been a rigorous national study of Montessori preschool education to inform how participating children fare. This first national study of public Montessori preschool programs follows over three years children whose families applied to 24 Montessori preschool programs via a lottery at age 3, comparing cognitive and socio-emotional outcomes of admitted and waitlisted students through their kindergarten year. Purpose/Objective/Research Question: The purpose of the study is to evaluate the effectiveness of public Montessori education in preschool and kindergarten compared to alternative early education settings. Specifically, we ask whether a public Montessori school admissions offer at age 3 impacts cognitive and socio-emotional outcomes by the end of preschool and kindergarten compared to children waitlisted at the Montessori school. Setting: The study was rooted in 24 public Montessori school sites across 13 localities in nine states. The schools had to have a lottery with a waitlist to qualify. Baseline data were collected in the fall of 2021 when children entered their first year of preschool (at age 3, henceforth PK3) with follow-up data collection at the end of PK3, preschool year two (PK4) and kindergarten (K). Population/Participants: The sample population is children who applied to attend a study Montessori at age 3. The fully consented sample of students includes 588 students (242 treatment and 346 control) nested in 30 lotteries (3 of the 24 school sites had multiple qualifying lotteries). Intervention/Program: The Montessori model is constructivist, holding that young children learn more by action than testimony. In Montessori classrooms, teachers serve as guides rather than primary knowledge sources. Teachers are responsible for providing prepared classroom environments filled with appropriate materials, and children have considerable freedom regarding which constructive activities they engage in; learning comes from appropriately interacting with materials. Because classrooms are multiage, children have opportunities to learn from and teach one another more so than in traditional single-age classrooms. Research Design: The study used a randomized lottery design with a waitlist control group. Children randomly selected for admission to a study Montessori school and whose caregiver consented to study participation were the treatment group, and those placed on the school's waitlist were the control group. One source of potential bias is systematic differences between treatment and control participants who denied study consent. To address this, we controlled for measures of the study outcomes at baseline and child and family background covariates. Differential missingness rates between treatment and control groups on assessment measures at baseline and follow-up is another source of potential bias; we used multiple imputation to limit this potential bias. Data Collection and Analysis: In the fall of 2021, students entering PK3 were assessed on early academic, executive function, and social-emotional skills. We used three subtests from the Woodcock-Johnson (WJIII) extended (Woodcock, McGrew, & Mather, 2001): two of literacy (Letter-Word Identification and Picture Vocabulary) and one of mathematics (Applied Problems). To measure executive function, we used the Head-Toes-Knees-Shoulders (HTKS) measure (Ponitz et al., 2008) and the Forward/Backward Digit Span task. To measure children's social-emotional skills, we used the Theory of Mind Scale (Wellman & Liu, 2004; Wellman, 2014), one object-acquisition story from the Social Problem Solving (SPS) Test--Revised (Rubin, 1988), and the Puzzle Task (Lillard, 2017) to measure mastery orientation. These child assessments were conducted again in the spring of the PK3, PK4, and K years by trained data collectors who maintained reliability and consistency on all assessment procedures. Montessori intent-to-treat (ITT) impacts were estimated using OLS regression with lottery fixed effects. We regressed the outcome on a treatment assignment indicator and controlled for the baseline measure of the outcome and the following baseline covariates: child sex, race, ethnicity, and primary language; household size; and caregiver education, marital status, and income. Complier average causal effect (CACE) analyses were performed to estimate Montessori impact for those who complied with treatment assignment, i.e., students who accepted their Montessori admission offer and would have enrolled in a non-Montessori absent the offer. CACE models were estimated using two-stage least squares regression with treatment assignment as the instrument and an indicator of study Montessori enrollment in either PK3 or PK4 as the endogenous treatment variable. Missing data were multiply imputed. Findings/Results: ITT results at end of K find that children offered Montessori admission scored statistically significantly higher, p < 0.05, on the WJ Letter-Word and Forward Digit Span measures and scored higher with results trending toward statistical significance, p < 0.10, for the WJ Applied Problems, HTKS, and Theory of Mind measures. Hedges' g effect sizes for these five outcomes ranged from 0.20 to 0.29. CACE models yield effect sizes roughly twice as large. We found no statistically significant effects at the end of PK3 or PK4. Conclusions: Children offered admission to a public Montessori preschool at age 3 scored statistically significantly higher at the end of kindergarten on measures of literacy and memory and scored higher with results trending toward significance on measures of math, executive functioning, and theory of mind compared to children placed on waitlists. These findings are consistent with smaller lottery studies of public Montessori preschool and indicate that for families who seek Montessori preschool, the ability to enroll through the public system can benefit the child's development (Courtier et al., 2021; Lillard et al., 2017; Lillard & Else-Quest, 2006). The study has three key limitations. Differential consent and assessment missingness between treatment and control groups may introduce bias in effect estimates, as mentioned previously. Also, schools were limited to those with admissions lotteries and waitlists that agreed to participate, so findings cannot be generalized beyond this sample of schools. Nonetheless, the study uses a rigorous randomized admissions lottery design with adjustment for baseline outcome measures and covariates, providing strong evidence on the potential benefits of public Montessori early education. |
| Abstractor: | As Provided |
| Entry Date: | 2026 |
| Access URL: | https://www.sree.org/2025-conference |
| Accession Number: | ED677748 |
| Database: | ERIC |
| Abstract: | Background/Context: Montessori preschool instruction in public schools is now widespread throughout the United States, with over 560 public Montessori schools, roughly a quarter of which start at age 3 (National Center for Montessori in the Public Sector, n.d.). Despite the widespread popularity of the model, until now there has never been a rigorous national study of Montessori preschool education to inform how participating children fare. This first national study of public Montessori preschool programs follows over three years children whose families applied to 24 Montessori preschool programs via a lottery at age 3, comparing cognitive and socio-emotional outcomes of admitted and waitlisted students through their kindergarten year. Purpose/Objective/Research Question: The purpose of the study is to evaluate the effectiveness of public Montessori education in preschool and kindergarten compared to alternative early education settings. Specifically, we ask whether a public Montessori school admissions offer at age 3 impacts cognitive and socio-emotional outcomes by the end of preschool and kindergarten compared to children waitlisted at the Montessori school. Setting: The study was rooted in 24 public Montessori school sites across 13 localities in nine states. The schools had to have a lottery with a waitlist to qualify. Baseline data were collected in the fall of 2021 when children entered their first year of preschool (at age 3, henceforth PK3) with follow-up data collection at the end of PK3, preschool year two (PK4) and kindergarten (K). Population/Participants: The sample population is children who applied to attend a study Montessori at age 3. The fully consented sample of students includes 588 students (242 treatment and 346 control) nested in 30 lotteries (3 of the 24 school sites had multiple qualifying lotteries). Intervention/Program: The Montessori model is constructivist, holding that young children learn more by action than testimony. In Montessori classrooms, teachers serve as guides rather than primary knowledge sources. Teachers are responsible for providing prepared classroom environments filled with appropriate materials, and children have considerable freedom regarding which constructive activities they engage in; learning comes from appropriately interacting with materials. Because classrooms are multiage, children have opportunities to learn from and teach one another more so than in traditional single-age classrooms. Research Design: The study used a randomized lottery design with a waitlist control group. Children randomly selected for admission to a study Montessori school and whose caregiver consented to study participation were the treatment group, and those placed on the school's waitlist were the control group. One source of potential bias is systematic differences between treatment and control participants who denied study consent. To address this, we controlled for measures of the study outcomes at baseline and child and family background covariates. Differential missingness rates between treatment and control groups on assessment measures at baseline and follow-up is another source of potential bias; we used multiple imputation to limit this potential bias. Data Collection and Analysis: In the fall of 2021, students entering PK3 were assessed on early academic, executive function, and social-emotional skills. We used three subtests from the Woodcock-Johnson (WJIII) extended (Woodcock, McGrew, & Mather, 2001): two of literacy (Letter-Word Identification and Picture Vocabulary) and one of mathematics (Applied Problems). To measure executive function, we used the Head-Toes-Knees-Shoulders (HTKS) measure (Ponitz et al., 2008) and the Forward/Backward Digit Span task. To measure children's social-emotional skills, we used the Theory of Mind Scale (Wellman & Liu, 2004; Wellman, 2014), one object-acquisition story from the Social Problem Solving (SPS) Test--Revised (Rubin, 1988), and the Puzzle Task (Lillard, 2017) to measure mastery orientation. These child assessments were conducted again in the spring of the PK3, PK4, and K years by trained data collectors who maintained reliability and consistency on all assessment procedures. Montessori intent-to-treat (ITT) impacts were estimated using OLS regression with lottery fixed effects. We regressed the outcome on a treatment assignment indicator and controlled for the baseline measure of the outcome and the following baseline covariates: child sex, race, ethnicity, and primary language; household size; and caregiver education, marital status, and income. Complier average causal effect (CACE) analyses were performed to estimate Montessori impact for those who complied with treatment assignment, i.e., students who accepted their Montessori admission offer and would have enrolled in a non-Montessori absent the offer. CACE models were estimated using two-stage least squares regression with treatment assignment as the instrument and an indicator of study Montessori enrollment in either PK3 or PK4 as the endogenous treatment variable. Missing data were multiply imputed. Findings/Results: ITT results at end of K find that children offered Montessori admission scored statistically significantly higher, p < 0.05, on the WJ Letter-Word and Forward Digit Span measures and scored higher with results trending toward statistical significance, p < 0.10, for the WJ Applied Problems, HTKS, and Theory of Mind measures. Hedges' g effect sizes for these five outcomes ranged from 0.20 to 0.29. CACE models yield effect sizes roughly twice as large. We found no statistically significant effects at the end of PK3 or PK4. Conclusions: Children offered admission to a public Montessori preschool at age 3 scored statistically significantly higher at the end of kindergarten on measures of literacy and memory and scored higher with results trending toward significance on measures of math, executive functioning, and theory of mind compared to children placed on waitlists. These findings are consistent with smaller lottery studies of public Montessori preschool and indicate that for families who seek Montessori preschool, the ability to enroll through the public system can benefit the child's development (Courtier et al., 2021; Lillard et al., 2017; Lillard & Else-Quest, 2006). The study has three key limitations. Differential consent and assessment missingness between treatment and control groups may introduce bias in effect estimates, as mentioned previously. Also, schools were limited to those with admissions lotteries and waitlists that agreed to participate, so findings cannot be generalized beyond this sample of schools. Nonetheless, the study uses a rigorous randomized admissions lottery design with adjustment for baseline outcome measures and covariates, providing strong evidence on the potential benefits of public Montessori early education. |
|---|
