With this study I investigate the consequential validity of a state English language proficiency (ELP) assessment, following Messick's (1989) expanded theory on validity. I examined intended and unintended consequences of the Texas English Language Proficiency Assessment System (TELPAS) through stakeholder perceptions. TELPAS is a federally required annual assessment used to measure the English proficiency of English learner (EL) students enrolled in public schools in Texas. TELPAS is a high-stakes test impacting over a million EL students and their campuses and districts (Texas Education Agency [TEA], 2020). In 2019-20, Texas planned for increased stakes regarding TELPAS as its role within state and federal accountability systems became more impactful due to implementation of new federal requirements under the Every Student Succeeds Act (ESSA, 2015). The law requires that states embed results from state ELP testing within state accountability systems (ESSA, 2015) eliminating multiple systems of accountability but increasing the stakes for ELP testing by giving it a higher profile. Research advocating more robust validity studies of ELP assessment instruments is needed (Chalhoub-Deville, 2020). With this study I contribute to such a body of research by conducting a mixed methods investigation, using survey research and semi-structured interviews, of aspects of the consequential validity of TELPAS. I explore key stakeholders' perceptions of the intended and unintended consequences of TELPAS. [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.]