This mixed methods study investigated the teachers' concerns of the sheltered instruction observation protocol (SIOP) model (Echevarria, Short and Vogt, 2008) as a means to differentiate instruction for LEP students in public school classrooms. This study took place in one central Georgia school district with a sample of 16 teachers who volunteered to participate in this study and completed surveys concerning the implementation and perceptions of the SIOP model. The sample of elementary teachers who participate had varied ranges of experiences and backgrounds which included bachelor's, master's and specialist degrees as well as varied types of certifications such as ESOL, special education, ESOL, reading, science and others. The concerns-based adoption model (CBAM) was utilized, which includes the levels of use survey (LoU), (Dirksen, George and Hall, 2008) and the stages of concern questionnaire (SoCQ), (George, Hall and Steigelbauer, 2008). The LoU and SoCQ were used to collect qualitative and quantitative data simultaneously. The sheltered instruction observation protocol (SIOP) checklist was utilized as a second instrument for quantitative data collection. The theoretical context related to research that focused on positive teacher concerns that facilitated positive delivery of differentiated instruction in the classroom setting for English language learners (ELLs). Based on the data collected using the LoU, the findings and conclusions are that not all teachers use the SIOP model as a means to differentiate instruction. The findings of the data collected from the SoCQ indicated that the sample of teachers in this study had high concerns relating to Stages 0-3 and low concerns relating to Stages 4-6. The SIOP observation tool findings indicated that not all teachers did use the SIOP model as differentiate instruction; however, the teachers did differentiate instruction by methods and strategies that were aligned to the SIOP model. [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.]