An outline is given of the context in which The International School Effectiveness Research Project (ISERP) was designed and it is argued that the deficiencies of existing studies and the increased internationalization of education makes the more rigorous approach of ISERP essential. A number of methodological lessons from the study are given, concerning the need for cohort studies, for observational data, for social outcomes data, for mixed methods, and for multiple indicators. The substantive lessons of the study for a strong technology of education, for a taken for granted in educational discussions within cultures, for societal support of education within cultures, and for a radical intellectual orientation are given. (Contains 2 tables.)