The 2001 reauthorization of the Elementary and Secondary Education Act (ESEA), No Child Left Behind, brought the use of student assessment data to the fore. This mandate-based and sanction-laden legislation ushered in a new era of accountability rooted in the collection, analysis, and use of student assessment data for educational improvements. As a result, a new boon industry has emerged around formative assessment products. This study begins by exploring the policies that have ushered in an assessment-driven accountability era. Then, the empirical and conceptual literature around the implementation and use of formative assessment systems is summarized. While there is promising literature on the effectiveness of formative assessment products, understanding what fosters or inhibits the use of assessment data for school teachers' needs further exploration. The purpose of this study is to understand if and how teachers are using formative assessment products or systems to impact their pedagogical decision-making in classrooms. This study will also focus on how school and district leadership teams choose or support the formative assessment system. In essence, this study seeks to investigate the fidelity of formative assessment products the actual impact used by schoolteachers; and more importantly, how data is transformed into information and ultimately knowledge. Research Questions: The research questions from this study are anchored in elements of fit, readiness, coherence, and use. Specifically, the intent of this research is to understand: (1) The district's intended purpose and the formative assessment system purpose of validity ("Fit"); (2) The capacity of teachers' to use formative assessment data to inform their pedagogical decision-making ("Readiness"); (3) The school district (and individual schools') ability to create, support, and resources the implementation and use of formative assessment systems ("Coherence"); And, (4) The actual use of formative assessment data by school teachers' in regard to pedagogical decision-making. Consequently, the study's research questions are as follows: (1) Are teachers and district/school leaders using the formative assessment data to inform educative decision-making and pedagogy? (a). How are teachers using these data to modify instruction/practice? (b) How are school leaders using these data for programmatic and in-service decisions? (2) Are the formative assessment products valid for their intended purposes? (a) Are the assessments used by the district valid for evaluating and improving instruction? (b) Are the assessments used by the district valid for measuring student progress? (c) Are the assessment used by the district valid for modifying teaching practices? (3) Are teachers ready and able to use formative assessment data in meaningful and effective ways? (a) How has the school district supported and resource the use of the formative assessment system? (b) How are teachers using these data to modify instruction/practice? Research Design: To answer the research questions, the research implements a three-phase design. To begin, phase one involves the identification of school districts in the state of Florida that have implemented a formative assessment system. These systems are examined to ascertain which are truly student-level diagnostic instruments (the Black and Wiliam (1998), definition of formative assessment was used to guide this analysis). Phase two documents why and how the formative assessment system was implemented into the district. Finally, phase three examines the actual use of the formative assessment system by teachers in the district. [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/en-US/products/dissertations/individuals.shtml.]