Abstract. We simultaneously resolve three paradoxes in academic self-concept research with a single unifying meta-theoretical model based on frame-of-reference effects across 68 countries, 18,292 schools, and 485,490 15-year-old students. Paradoxically, but consistent with predictions, effects on math self-concepts were negative for: • being from countries where country-average achievement was high; explaining the paradoxical cross-cultural self-concept effect; • attending schools where school-average achievement was high; demonstrating big-fish-little-pond-effects (BFLPE) that generalized over 68 countries, Organisation for Economic Co-operation and Development (OECD)/non-OECD countries, high/low achieving schools, and high/low achieving students; • year-in-school relative to age; unifying different research literatures for associated negative effects for starting school at a younger age and acceleration/skipping grades, and positive effects for starting school at an older age (“academic red shirting”) and, paradoxically, even for repeating a grade. Contextual effects matter, resulting in significant and meaningful effects on self-beliefs, not only at the student (year in school) and local school level (BFLPE), but remarkably even at the macro-contextual country-level. Finally, we juxtapose cross-cultural generalizability based on Programme for International Student Assessment (PISA) data used here with generalizability based on meta-analyses, arguing that although the two approaches are similar in many ways, the generalizability shown here is stronger in terms of support for the universality of the frame-of-reference effects.