Action research is characterized by research that is done by teachers for themselves. It allows teachers to study their own classrooms in order to better understand them and to be able to improve their quality or effectiveness. Montessori modeled and laid the foundation for teachers to carefully observe, reflect on their observations, plan for positive change, implement a plan, and then start the cycle again: Observe and evaluate the outcome, and reflect, plan, etc. Through this cycle, she was modeling what it means to be a reflective practitioner--open to positive change in order to effectively meet the learning needs of their students. This article reviews of how Maria Montessori modeled action research, and an exploration into how it can utilized, not just for improved effectiveness in the classroom but for social justice.