This article presents evidence for a validity argument on the ACTFL Assessment of Performance Toward Proficiency in Languages (AAPPL) tests (Interpersonal Listening/Speaking, Presentational Writing, Interpretive Listening, and Interpretive Reading) by summarizing an analysis of the 2014 test data from examinations administered in three languages (Chinese, French, and Spanish) to more than 10,000 students in grades 5 to 12. The specific stages the authors evaluated included the following: (1) the design of the instrument, (2) the effectiveness of the rating scale, (3) the reliability of the instrument, and (4) the extent to which ACTFL proficiency levels were generalizable across languages. As a complete test battery, there is validity evidence that the Assessment of Performance Toward Proficiency can be used to measure the performance of upper elementary, middle, and high school students as they develop increasingly sophisticated language proficiency. The strengths of the examinations are the productive skill areas, whereas the receptive skill areas have been targeted for continuing development.