In the US K-12 public school settings, each state's annual English language proficiency (ELP) assessment, as part of an educational accountability system, has tremendous impact on English learner (EL) students' academic paths and success. It is thus critical to establish a robust validation framework and empirical evidence to ensure that states' ELP assessments are both appropriately interpreted and justifiably used for their intended purposes. The present article, as a perspective piece, highlights two key interrelated areas of validity concern: the construct and the consequences of ELP assessments. This article describes how the ELP construct has been redefined and operationalized in recent K-12 ELP standards and assessments in the US K-12 education settings, reflecting the current US educational reform and policy impact. Then, the article presents the ramifications these new ELP assessments have for making high-stake decisions about EL students and how construct validity issues are closely tied to consequential validity. A set of pivotal research areas pertaining to construct and consequential validity is proposed with implications for practice and policies to support EL students' needs. Implications from interconnection between the construct and the consequences of ELP assessments and research areas suggested in this article can be applicable in other countries where language assessments are part of educational reform or accountability systems.