Strengths and weaknesses of different research approaches are discussed, and it is proposed that the dichotomy between qualitative and quantitative approaches should be replaced with distinctions between low- and high-level inference approaches with respect to data, generalization and explanation. It is concluded that while the international studies easily invite misuse and misinterpretation, they also offer possibilities for improving the quality of educational research, because the high-quality data generated by these studies can be taken advantage of in research on causal effects of factors in and out of educational systems.