English Learners (ELs) are students whose native language is any language other than English. ELs participate in language acquisition programs throughout the United States to help the attainment of English proficiency. ELs are also expected to acquire the English language while performing at the same academic success as their native English classmates (Echevarria et al., 2017). High school teachers of English Learners (EL) of an urban high school in the Southeastern region of Texas raised concerns regarding ELs not becoming proficient in the English language and not exiting the EL program enabling ELs to be mainstreamed into the regular classroom population. The purpose of this proposed study was to explore the academic development of high school ELs and to explore whether high school teachers felt sheltered instruction (SIOP model) and being culturally sensitive to EL students contributed to the linguistic and academic development of ELs. It is unknown in the research proposal whether the implementation of the SIOP had a significant effect on the academic development of high school ELs and if high school teachers were implementing EL instructional strategies with cultural sensitivity and 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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]