How to conceptualize teaching quality in the future: some confirming, some complementary, and some critical remarks, and some of them hopefully helpful

This commentary discusses whether the problem motivating this special issue, that is, the frequently small and inconsistent effects of teaching-quality indicators, is the main problem of research on teaching quality. The core problem might actually be a suboptimal theoretical foundation, a common problem in research on learning and instruction. Against this background, one of the main strengths of this special issue’s articles is that they elaborate on the importance of theory. They describe very profound analyses of the shortcomings of past and current research on teaching quality, leading to highly ambitious proposals for future research. However, we also need to define realistic, doable goals to advance research on teaching quality in the near future. For this purpose, we propose a type of argumentative validity perspective on teaching quality, that is, developing conceptualizations of teaching quality that are valid when addressing specific research goals.