It is the moral responsibility of educators to work diligently to provide every student with rich, challenging coursework in efforts to prepare them for post high school careers and education. The use of common formative assessments provides teachers with the valuable, timely information they need to make instructional decisions that will better support the learning of all students. The purpose of this study was to determine staff members' perceptions of the implementation and effective use of common formative assessments in a progressive upper elementary school in the Midwestern United States. This study also sought to discover the types of leadership that facilitate the effective use of common formative assessments, and explored the cultural ideals and beliefs that contribute to the effective us of these assessments. The conceptual underpinnings of this study included social justice advocacy leadership, a culture that fosters growth and achievement for all learners, and assessment that supports every child. Research questions were developed to ascertain the effective practices this school used to implement common formative assessment that contributed to sustained achievement in mathematics. This study also sought to to discover the types of leadership and cultural characteristics that contributed to the effective use of these assessments. This instrumental, qualitative case study analyzed the perceptions of third, fourth, and fifth grade level teachers through six focus group discussions. In addition three leadership interviews were conducted that involved the building principal, instructional coach, and school counselor. An open-ended survey gleaned additional insights from the instructional staff at this progressive upper elementary school. Several documents pertinent to the study were analyzed. Evidence indicated the implementation of common formative assessments in this school did contribute to sustained mathematics achievement. Three major themes emerged: (a) focus and alignment of curriculum, instruction, and assessments, (b) using data to drive instruction, and (c) differentiating instruction to meet student learning needs. Four predominant types of leadership facilitated the implementation and effective use of common formative assessments (a) renewal leadership, (b) moral/ethical leadership, (c) instructional leadership, and (d) distributed leadership. Cultural characteristics that emerged as having significant contributions included: (a) reculture, (b) collaboration, (3) high expectations, and (d) caring relationships. Implications for practice were discussed for each emergent theme in regard to implementation and use, leadership, and culture. This study was significant as it describes the common formative assessment practices, types of leadership, and cultural characteristics of an upper elementary school who has effectively implemented common formative assessments and has experienced a 29% gain in mathematics scores since implementation. Discussion of study findings would be useful for school leaders seeking to implement common formative assessments in efforts to increase student 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.]