Public school teachers are at the forefront of education in the United States; they must employ methods such as data-driven decision making (DDDM) to ensure that all students are learning. Quality decision making is vital in this age of accountability under the No Child Left Behind Act (NCLB) that includes mandated state testing such as the Criterion-Referenced Competency Test (CRCT) in Georgia. It is essential to understand the lived experiences of teachers regarding data use for instructional design particularly related to training, implementation expectations, and use because these experiences may determine how effectively teachers will utilize test data. Furthermore, researchers have not documented these experiences in prior literature, thus precipitating a need for this study. In this qualitative phenomenological study, individual interviews were conducted with six teacher participants purposefully selected from middle schools in northeast Georgia. Participants included language arts and math teachers of students classified as regular, gifted, and special education from grades 6 through 8 with varying levels of education and experience. The interviews detailed the lived experiences of teachers related to training, implementation expectations, and use of CRCT data for planning and designing instruction. The major conclusion of this current phenomenological study was that CRCT data was not being utilized by teachers to plan day-to-day instruction. An additional conclusion was that the total lived experiences of teachers as a whole including several impediments negatively impacted and inhibited teachers from utilizing CRCT data to plan day-to-day instruction. Therefore, it is recommended that the impediments to effective implementation of DDDM practices defined in this study be addressed to increase the likelihood of improved student success in the future. Policy implications from this study may include changes to (a) teacher training practices regarding data use, (b) expectations and mandates regarding teachers' data use, (c) teacher evaluations incorporating data use, and (d) the usability and timeliness of CRCT data. Recommendations for future studies include studying (a) teacher data use from other large-scale tests other than the CRCT, (b) which data teachers currently utilize effectively, and (c) administrators' perceptions of teacher data use in comparison to actual teacher data use. [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.]