This paper reviews the most known international assessment studies that are conducted in the context of poor countries and highlights the lack of empirical evidence on the degree to which the contents of the tests really match countries' curricula. To illustrate, the paper evaluates the sensitivity of an international testing instrument by comparing the responses of students in two consecutive grades on the same battery of tests. Using propensity score matching to control for student and teacher characteristics, the results show that the tests are not grade sensitive, which raises the question of the validity of many empirical works that are based on similar instruments.