The research centered on secondary mathematics teachers' beliefs, attitudes, knowledge base, and practices in meeting the academic and language needs of English language learners. Using socio-cultural theory and social practice theory to frame the study, the research design employed a mixed methods approach incorporating self-reported surveys, observations, and interviews of secondary mathematics teachers at a large South Texas suburban school district. The results indicated the secondary mathematics teachers having a generally positive belief about the capabilities of English Language Learners (ELLs). The teachers expressed knowing instructional strategies that addressed language and academic needs of ELLs. The inconsistencies to enact instructional practices that met ELLs' needs evolved from the emergent themes based on the data. The knowing-doing gap represented the barriers and opportunities to empower beliefs and knowledge into actions. The importance of communication emerged as both an agency and influential factor along with other socio-cultural factors, such as the testing culture, lack of resources, and differences of language and cultures. The findings direct researchers to support secondary mathematics teachers, administrators, and teacher educators with shared learning experiences toward shifting beliefs, transitioning attitudes, and increasing knowledge base in order to implement high-yield ELLs' instructional strategies with fidelity. [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.]