Critical reviews from “outside”, notably educational sociologists arguing mainly from a British context, have caused some ripples, and maybe even waves, among school effectiveness researchers. To a large extent these external criticisms and the overall nature of the response from school effectiveness researchers are neatly summarized in the following quote from Townsend: “be like us”, say the critics, and the answer is “no thanks”. In this article the arguments form the “external” critics and the response from school effectiveness researchers will not be repeated. Some of the topics in the debate will be revisited, however. The first one is the discussion with respect to the impact of “contextual” or composition effects concerning the average socioeconomic background of students in schools and classrooms. This is one area, that bears upon the foundations of the school effectiveness concept, although it is not, as the critics would have it, a neglected area. The second one concerns conceptualization and theoretical explanation of school effectiveness, as the debate may not have been sufficiently explicit on this issue. The rest of the paper deals with “foundational” issues in school effectiveness research that have not been settled decisively and with changes in perspectives on learning and instruction and educational technology that provide serious challenges. On these issues there is reason for self-criticism and realism in the way school effectiveness research can make progress.