English language learners continue to be a growing demographic in American schools. Despite this, linguistically diverse students’ academic achievement continues to lag behind their native English-speaking counterparts. Historically, language proficiency measures have measured language proficiency in terms of social English, neglecting the importance of academic language development. Using Cummins’ threshold hypothesis as a framework for distinguishing social English development from academic language development, language proficiency assessments and standardized assessments focused on reading achievement were examined. The purpose of this quantitative, correlational study was to determine if a relationship exists between 5th grade English language learners scores on a state-mandated standardized assessment and a language proficiency exam that measures academic language development. The instruments used to conduct this study were the 5th Grade North Carolina End-of-Grade Reading Test and the World-Class Instructional Design and Assessment (WIDA) Assessing Comprehension and Communication in English State to State (ACCESS) language proficiency exam. Participant scores from a suburban school district in North Carolina during the 2018–2019 school year were used. The results from the study demonstrated there was a significant relationship between academic achievement as measured by the North Carolina EOG reading test and language proficiency as measured by the WIDA ACCESS exam for fifth-grade English language learners. Recommendations for further study include examining English language learners scores across a range of content areas.