This case study offers an in-depth look at how one school achieved change in its culture and in its approach to curriculum and instruction. The unit of analysis for this single case study is South Loop Elementary School (SLES) and the time period is from August 2002 to June of 2007, during which SLES students demonstrated sharply improved achievement on the Illinois Standardized Achievement Test. The study seeks to answer the question How did a high-need urban elementary school use standardized and formative assessments in an effort to improve student learning in literacy? Data demonstrate how SLES's use of data from assessment cycles contributed to school change at SLES. This work, emphasizing the use of formative assessments, engaged teacher teams in the analysis of student assessment data, including student writing. The study provides a potential model that is consistent with school improvement theory and is specific about systems and structures that could be adaptable to any school community to support teacher focus on improving student learning. This study examines how teacher learning was supported in professional learning communities in one school that dramatically improved student learning outcomes over a five year period. In this model, teacher learning is supported through the study of assessments and the collaborative effort to improve instruction. [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.]