Elementary education has theoretical underpinnings based on cognitive psychology. Ideas from cognitive psychologists such as James, Dewey, Piaget, and Vygotsky coalesce to form constructivism (Cooper, 1993; Yager, 2000; Yilmaz, 2011). Among others, the Montessori Method (1912/1964) is an exemplar of constructivism. Currently, public education in the United States is heavily impacted by the No Child Left Behind legislation (Paige, 2006) which emphasizes high stakes academic achievement testing. Absent from the literature is an examination of the academic achievement of Montessori students in public education. This study explores the academic achievement outcomes of public school students who completed varying numbers of years in Montessori elementary education. Singer and Willett's (2003) multilevel model of change serves as the statistical tool utilized to explore the academic achievement outcomes of a first grade cohort through their elementary and secondary school careers. Accrued years in Montessori did not account for significant variance amongst the trajectories, and gender and ethnicity, when considered without the interactions with accrued years, had minimal impact. Socioeconomic status, when the variable of accrued years in Montessori was removed from the equation, was a significant predictor of reading and math achievement. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]