International student assessments measure student achievement, attitudes, opinions, well-being, and other aspects of their life and schooling. These measures are compared internationally across countries and time to inform policymakers and teachers. We discuss the reliability and comparability of crucial results from studies like PISA and TIMSS. We argue that many results can be trusted, given their correct interpretation. However, we also give examples of doubtful but popular findings which misguide ministers of education, experts, and teachers. We focus on PISA’s attempt to measure student well-being and preferences towards learning modes. We show how PISA results drive us to see meaning where there isn’t any. Finally, we present research tools implemented in Poland to measure student preferences and well-being in a highly reliable way and how we work with teachers to use these results in their classrooms.