The TOEFL Junior Standard test is a tool for measuring the English language skills of students ages 11+ who learn English as an additional language. It is a paper-based multiple-choice test and measures proficiency in three sections: listening, form and meaning, and reading. To date, empirical evidence provides some support for the construct validity of the TOEFL Junior Standard test as a measure of progress. Although this evidence is based on test scores from multiple countries with diverse instructional environments, it does not account for students’ instructional experiences. The present paper aims to provide additional evidence by examining the TOEFL Junior Standard test as a progress measure within the same instructional setting. The study took place in an after-school English program in Armenia, a non-English-speaking country. A total of 154 adolescents took the TOEFL Junior Standard test three times with different test forms at the intervals of 10 and then 20 instructional weeks (a total of 30weeks). The difference in differences (DID) analysis shows that TOEFL Junior is sensitive to learning gains within 20 instructional hours per 10weeks among A1–A2 level learners, according to the Common European Frame of Reference (CEFR) scale. However, the data did not provide support for this sensitivity among B1–B2 level learners even though their instructional time was twice as long. Although this methodology offers an improved control over the students’ instructional experiences, it also delimits the results to a specific after-school program and comes with a set of other limitations.