This study explores reflective practice of Japanese elementary school teachers in teaching English. In Japan, English education is new in elementary schools as it started to be taught as a formal subject since 2020. Therefore, elementary school teachers are still not confident with teaching English to children and need to be established a solid professional development program for the teachers. Drawing on a constructivist framework of teacher learning and development, this study proposes that reflective practice, which involves teachers accumulating knowledge and improving their pedagogy by interrogating and modifying their teaching practice (Crandall, 2000; Kaufman & Brooks, 1996), could help Japanese elementary school teachers to examine their teaching and ideologies of English. Due to the history of English imperialism in Japan, Japanese people have an inferiority complex toward English (Clark, 1998; Kubota, 1998; Tsuda, 1990). Teachers with sufficient teaching experience suffer from feelings of inferiority toward their English proficiency, creating an obstacle to confident teaching (Otsuki, 2010). Under such circumstances, reflective practice could break their inferiority complex by revaluing their beliefs toward English and examining the goal of English teaching. Focusing on a case of four Japanese teachers in public elementary schools in Japan, the pilot study found that there was an already existing form of reflective practice in Japan, known as "Hansei" ([Japanese characters omitted]): to reflect on one's behaviors, focusing on mistakes and blaming oneself (Otsuki, 2018; 2019). However, "Hansei" focuses on unsuccessful points and makes teachers isolated from one another and worsens their feelings of inferiority. Therefore, this study looks into how teachers could engage in reflective practice more positively by rethinking their values around English education. As an intervention, the study provided monthly teacher education sessions in the target school. The teacher education sessions called MET (School M's English Training). MET 1) was led by an outside specialist so that only specific teacher/lesson could not be a target to be examined, 2) had plenty of opportunities of discussing with other teachers, and 3) the discussions were mainly about teachers' current practice, concerns, and teaching ideas useful in the near future rather than focusing on lessons already done. MET was organized in contrasted with the traditional lesson study approach widely implemented in K-12 schools in Japan (Miura, 2011). Three teachers in the school were followed over about one academic year to investigate their transformation of reflective practice and ideologies of English teaching. The findings revealed that, based on the teacher education sessions, the participant teachers were actively conducting collaborative reflection with other teachers and were encouraged by the very positive atmosphere among the teachers at the school. In addition, the teachers felt more positive about their teaching English. This study will benefit struggling Japanese elementary school teachers in offering an efficient but meaningful process for engaging in more culturally-tailored reflective practice and broaden scholars' and educators' perspectives toward the goal of English education and the transformative potential and limitations of reflective practice as a theory and practice. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]