In this article, Graham Nuthall critiques four major types of research on teaching effectiveness: studies of best teachers, correlational and experimental studies of teaching-learning relationships, design studies, and teacher action and narrative research. He gathers evidence about the kind of research that is most likely to bridge the teaching-research gap, arguing that such research must provide continuous, detailed data on the experience of individual students, in-depth analyses of the changes that take place in the students' knowledge, beliefs, and skills, and ways of identifying the real-time interactive relationships between these two different kinds of data. Based on his exploration of the literature and his research on teaching effectiveness, Nuthall proposes an explanatory theory for research on teaching that can be directly and transparently linked to classroom realities.