Teachers who have inadequate training often feel unprepared to teach English language learners (ELLs). This qualitative case study's purpose was to reap a rich understanding of middle school teachers' perceptions, perspectives, and prior teaching experiences concerning their capacity to instruct ELLs in the mainstream setting. The overarching research question addressed the perceptions, perspectives, and prior teaching experiences of middle school teachers who have taught ELLs. The theoretical foundation for this study drew from Vygotsky's Zone of Proximal Development with respect to both language acquisition and equitable teaching practices suited for an ELL's educational needs. Criterion sampling was employed to select 10 participant interviewees who had a minimum of 1 year of experience teaching ELLs. In addition to interview data, unobtrusive data consisted of standardized achievement scores, English proficiency levels, and a school improvement plan. The qualitative analysis technique consisted of epoche, reduction, horizonalization, themes, and reflection. Results of this study concluded that participants felt inadequate in their abilities to accommodate ELLs in the mainstream setting and led to the design of professional learning opportunity sessions intended to promote teacher effectiveness in today's diverse classroom. The literature conveyed teachers who are empowered to instruct ELLs can promote an advantageous learning environment; thus, ELLs' academic achievement can prosper. When professional learning opportunities are available to teachers, a more equitable learning environment will exist for ELLs and will provide opportunities for social change. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]