Although numerous English language proficiency (ELP) measures currently exist, many were developed prior to the No Child Left Behind Act of 2001 (NCLB). These pre-NCLB measures typically focused on social language proficiency, whereas post-NCLB measures are linked to ELP standards and focus on academic language proficiency (ALP). ELP measures are typically used for accountability purposes and to determine eligibility for services; less attention has been given to their utility in enhancing classroom instruction and intervention provision. Inconsistency in scores between pre- and post-NCLB measures frequently leaves educators wondering whether English language learners (ELLs) have the necessary ALP to benefit from classroom instruction. This study investigates the intervention validity of ELP assessment by examining the concurrent validity of various pre-NCLB measures to a recently developed post-NCLB measure. As hypothesized, results indicate moderate correlations between pre- and post-NCLB measures, suggesting that ALP-focused post-NCLB measures are likely to provide more utility for ELL classroom instruction and intervention provision. (Contains 8 tables.)