International comparative studies in education offer several elements of complexity, concerned with either survey methodology and procedures or the interpretation of results, that are highly debated among specialists and often not thoroughly considered by mass-media and policy makers, especially in Italy. Following the baconian scheme of pars denstruens and pars construens, this article proposes firstly a series of criticisms highlighted in the past about international surveys and then some of the most recent developments in the field, in order to remove, as far as possible, the idola theatri which obstacle a clear understanding of these contributions.
Keywords comparative studies, IEA ICCS, OCSE-PISA, opportunity to learn, cultural biases.