The purpose of this study is to observe the relationship between the partial or total use of Montessori education (ME) and academic (literacy, numeracy) and developmental (executive functions) outcomes in 105 French Kindergartners (children in preschool’s final year, [M = 5.53 years, SD = 0.29]). We conducted a quasi-experimental study comparing three groups. The first group (n = 48[18 girls], M  = 5.53 years, SD = 0.29) used a conventional teaching method, the second group (n = 40[21 girls], M  = 5.56 years, SD = 0.28) partially used the ME in addition to the conventional method, and the third group (n  = 17 [7 girls], M = 5.42 years, SD = 0.29) fully implemented the ME. Equivalence between the experimental and control groups has been verified in terms of age, gender, overall cognitive ability, and socioeconomic background. We assessed children’s competencies in early literacy, early numeracy, and executive functions. Results show better outcomes in the numeracy and inhibition control tests in the fully ME group, followed by the partial ME group. The group of children who had received conventional education obtained the lowest results. Finally, the differences in literacy scores were not significant.