The purpose of this mixed-method study was to examine elementary teacher perceptions of mandated curriculum change. In the spring and fall of 2015, Illinois elementary school teachers in a north suburban school district participated in a focus group, an online survey, and follow-up interviews to gather data about teachers' perceptions of the mandated curriculum change process in implementing the Common Core State Standards in English language arts and mathematics. The study also sought to find any differences between the perceptions of teachers in kindergarten through fifth grade classrooms and those who taught in sixth- through eighth-grade classrooms. This study was based on a conceptual framework that included three different theorists, which provided a comprehensive lens to review the data: Knowles's Adult Learning Theory; Fullan's Three-Tier Change Process; and Au, Raphael, and Mooney's Model for Standards-Based Change. Using the combined work of these three theorists, three key overlapping components were validated within this research when implementing a school or district-mandated curriculum change. [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.]