Over the last two decades, there has been renewed interest in formative assessment, in large part due to the increasing pressures and prevalence of "high stakes" summative assessments. As states try to meet the requirements of the No Child Left Behind law, teachers and administrators are realizing that formative assessment offers an effective means of increasing student achievement and identifying specific learning gaps. In response to this recognition, many companies and institutions have designed online programs to assess students formatively. However, there has been little empirical research in how teachers use these programs in their planning and instruction, especially in the field of English Language Arts. This study examined how four middle school English Language Arts teachers used information generated by one or more online formative assessment programs to plan and implement reading instruction in their classrooms. The overarching research question for the study was: What is the impact of online formative assessment in reading on teachers' planning and instruction in the middle grades English Language Arts Classroom? (Abstract shortened by ProQuest.) [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.]