The analysis of (inter)national large-scale assessments (LSAs) promises representativity of their results and statistical power and has the ability to reveal even minor effects. LSAs' international grounding verifies previous findings that might previously have been biased by their focus on Western and industrialized countries. This contribution will discuss these promises, contextualizing them via methodical challenges and interpretation caveats that are able to tap the potential of LSAs for educational psychology. Evidence of this contribution is grounded in previous analyses of Program for International Student Assessment (PISA; Schleicher, 2019) and Program for the International Assessment of Adult Competencies (PIAAC; OECD, 2013), two internationally repeated cross-sectional studies. Many aspects we bring up can also apply to several other international large-scale studies, such as TIMSS, PIRLS, and ICILS. We also refer to the national longitudinal study German National Educational Panel Study (NEPS; Blossfeld et al., 2011) to include a perspective on longitudinal studies in this paper. Implications for large-scale studies within the context of learning and teaching round off our paper in its closing section.