While such recent legislation as the No Child Left Behind Act (NCLB) mandates monitoring the progress of all students--including English language learners (ELL)--the validity and fairness of assessment tools for such students remains a major concern for educational researchers and practitioners. The rapid increase in the number of ELL students nationwide makes these concerns even more profound. Results from a series of UCLA/CRESST studies have clearly demonstrated the effect of language factors on assessments, particularly for ELL students. This article presents the summary of the results of the CRESST-sponsored studies. The results suggest that language modification of test items can be used as an effective and valid accommodation for English language learners. It is effective because it reduces the performance-gap between ELL and non-ELL students. It is valid because it does not alter the construct being measured, that is, it does not affect the performance of high-performing non-ELL students. Further, the linguistically modified test version is a feasible form of accommodation because it does not cause any additional burden on the instruction or assessment of the students being tested.