English Learners (ELs) in mainstream classrooms must overcome additional language barriers to comprehend and master Common Core State Standards in mathematics. I will be working as a teacher after graduation who will provide content-based instruction to ELs in Spain and Phoenix, AZ. As someone who will be graduating with non-education degrees but working in education, it is imperative that I understand the best methods to create a conducive learning environment for simultaneous L2 acquisition and content comprehension. After reviewing previous research, I identified multiple methods that assist ELs in simultaneously acquiring classroom content and improving English Language Proficiency (ELP). I have used these methods to construct three lesson plans that teach three mathematics standards and corresponding ELP standards for third-grade students in Arizona. I analyzed the methods that were used in my lesson plans and expanded upon how they will enhance ELP for ELs in my classroom. I have concluded my report by identifying some shifts in Common Core State Standards and the implications that these shifts have for ELs in mainstream classrooms.