Students with different abilities perform lower on state standardized tests, such as the STAAR test (Texas Education Agency, n.d.). The purpose of this qualitative multiple case study was to study the underlying causes that contributed to the low performance of students with different abilities on STAAR standardized tests and strategies the teachers in the State of Texas use to prepare students with different abilities. For this study, students with different abilities include students with special needs, students from economically disadvantaged families, and English language learners through the perception of middle school teachers. The theoretical framework for this multiple case study was Bronfenbrenner's bioecological systems theory (Sanjayan et al., 2020). The literature review provided an in-depth examination of what factors influence different ability students and their efforts to show mastery of concepts on standardized tests such as STAAR. Teachers from two middle schools provided data by taking part in semi-structured interviews. Twenty participants were selected from two middle schools for this study. The themes that emerged from the data analysis included: (a) lack of exposure, (b) language barriers, (c) the student's disability, and (d) instructional strategies used to teach students with different abilities. The implications of the study were that the vast majority of students measured for content mastery based on grade level criteria while failing to account for the different abilities of students and their accommodations. Recommendations for practice include offering differentiated assessments to measure students' mastery of concepts covered with suitable supports and accommodations and providing professional development on the instructional strategies used in the classroom for students with different abilities. Recommendations for future research include conducting quantitative research to analyze the students' performance on standardized tests, focusing on the performance of students with different abilities. Another recommendation for future research would be a qualitative study on teachers' perspectives from other states than Texas and teachers' focus on instructional strategies educators use to teach students with different abilities. [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.]