This article is a tribute to Graham Nuthall's contribution to classroom research from his early experimental studies through to his recent work on theory integration. It also explains the potential of the methodology, findings and theory building in our collaborative work to make a substantial positive difference for diverse students. The article explains the significance of, and need for, research linking learning to teaching processes (a scientific realist approach to putting "process," socio-cultural context and theory building into a new process--product paradigm). Findings of student outcomes contrary to educational goals (for example, teaching designed to enhance appreciation of cultural differences triggering racist abuse) signal the importance of research that explains the impact of teaching on learner outcomes. The article also foreshadows the implications of the work that Graham and I did for teaching, teacher education, research and educational policy. The article concludes with Graham's view that the most important contribution his work would make, would be to initial teacher education.