These findings strongly indicate that the sizeable effects of school-level SES reported from analyses of PISA data would not survive controls for prior ability and, to a much lesser extent, school-level prior ability. The analyses presented in this paper do not support arguments that school-SES has strong effects on student achievement and that its effects warrant a policy response. This is not to say that school-level SES effects are trivial in other educational jurisdictions but studies similar
to this one, controlling for student and school prior ability, would establish their magnitude and relevance to policy discussions.