Formative assessment, assessment for learning, involves checking in with students during the learning process to see if they understand concept or standard, before holding them accountable for mastery and moving on to the next concept or standard. This process can be used in the classroom during the lesson or across a subject area as teachers of the same subject create and administer common formative assessments and then use the data to make instructional decisions before moving on. Research has shown increases in student achievement with the use of formative assessment. The problem with formative assessment, however, is that it is defined in different ways. There is not one consistent definition across the educational spectrum. In addition, at the classroom level, teachers tend to be more comfortable with traditional ways of teaching and hesitant to incorporate new strategies that enable them to check in with every student throughout the lesson. Across the subject area, there are issues such as a lack of a collaborative structure within the school that allows teachers to regularly work together on assessments and data analysis. There is also the problem of teachers not knowing how to analyze the data and draw conclusions. For some, there is a lack of comfort in the sharing of data with colleagues.The purpose of this qualitative study was to explore the use of formative assessment and the resulting data to drive instruction in the classroom. The researcher sought to understand the experiences of classroom teachers as they implement formative assessment in the classroom, use the assessment data to see where the students are in the learning process, and, ultimately, use the data to make decisions about what to do next for the learners. This study involved six middle school teachers at two schools in a rural school district who were identified by their principals, testing coordinators, and instructional coaches as the best in the school for implementation of formative assessment in the classroom. The researcher used observations and interviews to investigate the following research questions: (1) How do teachers implement formative assessment in the classroom?; (2) How do teachers use formative assessment data to make instructional decisions?; and (3) How were the teachers trained in the use of formative assessment? The study revealed the same issues found throughout the literature on formative assessment. A variety of definitions exists, even among teachers in the same school and district. Some teachers are still tied to tradition in the way they deliver lessons and check for understanding. There is a lack of collaboration among colleagues, which prevents effective use of formative assessment across subject areas. There also exists a lack of training on the use of data to make instructional decisions. The study revealed the need for school leaders at all levels to learn about and embrace the concept of formative assessment and build cultures within schools where formative assessment is an expectation and in which instructional leaders facilitate the process. [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.]