This study examines teachers' beliefs in relation to their roles with respect to K-12 students with English as an additional language and co-existing disability (SEAL+D) participation in state-mandated accountability assessments. U.S. federal laws of the Elementary and Secondary Education Act (ESEA), last reauthorized as the Every Student Succeeds Act of 2015 (ESSA), and the Individuals with Disabilities Act of 2004 (IDEA) require states to report on students' test outcomes for English learners and students with disabilities in meeting academic content standards in state assessments. For these tests, SEAL+D, who have both designations, must also participate. Title I and III of ESEA specifically mandate that English learners with disabilities, i.e., SEAL+D, participate in their state's English language proficiency assessments. However, more understanding is needed about the participation of SEAL+D in these tests. This study addressed this gap with asynchronous online focus groups conducted with teachers from a Midwestern state. Thematic analysis of these data through the lens of language policy and intersectionality indicates that teachers broadly shared similar beliefs about the mismatch between the linguistic complexity of the tests and their expectations of students' abilities. Moreover, input from English language teachers concerning students' academic English language proficiency was often not included in a student's special education individualized education program (IEP) team. The exclusion of the consideration of academic English language proficiency in the IEP has implications for students to meet academic standards. [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.]