In recent decades, the landscape of the U.S. classroom has been drastically changing. Schools at every level are enrolling increasingly higher numbers of culturally and linguistically diverse learners, many in the process of learning English. These students, frequently called English language learners (ELLs), present new and unique challenges to educators. Many of these challenges concern language and the many ways it affects the educational experience. One concern of great interest involves better understanding the ways language and academic content interact. Language is a pivotal component of the learning experience, and likely to affect students’ perceptions of the classroom environment and themselves, as well as interactions with teachers and peers. This concern remains critical to consider in secondary mathematics, where language demands are high, but teachers may not be trained to attend to both language and content in the mainstream classroom. The present research used data from the High School Longitudinal Study of 2009 to investigate the secondary mathematics experiences of ELL and non-ELL students in two studies conducted at distinct levels: student and teacher. At the student-level, hierarchical linear modeling was used to compare the effects of several student variables on both access to and achievement in mathematics, as well as how these effects differed between ELL and non-ELL students. Findings indicated that both mathematics self-efficacy and interest in early coursework were positively related to access to and achievement in mathematics, and these relationships were significantly stronger for ELL students. Conversely, positive perceptions of the learning environment and classroom engagement were often related to gains in outcomes for non-ELL students, but decreases for ELL students. This study highlighted several key factors of the secondary mathematics experience that behaved differently for ELL and non-ELL students. Implications of these findings are further discussed in Chapter 2. At the teacher-level, hierarchical linear modeling was used to compare the effects of teacher experience, classroom practices, and perceptions of departmental support on the access to and achievement in mathematics of their students, and how these effects differed between ELL and non-ELL students. Findings indicated that more conceptually-oriented teaching practices were beneficial to both students, with greater gains long-term for both ELL and non-ELL students. Procedurally-oriented teaching was beneficial to ELL students in nearly all cases, but detrimental to non-ELL students’ mathematics outcomes. The effects of perceptions of departmental support varied, with mixed effects for some (e.g. principal support) and detrimental effects for others (e.g. sense of responsibility). Implications of these findings are further discussed in Chapter 3. Finally, Chapter 4 discusses overarching themes across studies at both levels, summarizing the results with regards to student variables, teacher variables, and student-teacher-school relationships. Implications for administrators, teachers, and teacher educators are discussed.