Test anxiety has proliferated in the era of test-based accountability; however, there are limited tools that allow for consistent identification of students at risk. The present study reports on the psychometric evidence and continued development of the Multidimensional Test Anxiety Scale (MTAS). Evidence is presented to support both the interpretation and use of the MTAS. The present sample included over 900 high school aged students across England and Wales that completed a measure of test anxiety and clinical anxiety. Results from confirmatory factor analyses, measurement invariance, and internal consistency support the interpretation of the MTAS. In addition, receiver operator characteristic curve analyses were used to identify initial cut scores to support decision-making in applied settings. Results for practice and future research are presented.