Launched at the beginning of the 21rst century, PISA surveys (Programme for international student assessment) whose have been a part of a specific European context, whose purpose is to establish a European policy in the education field, and are characterized by the development of a soft governance through benchmarking, that is a supposed suggestive one only, based on comparative indicators, supposed to foster a sound emulation. After having rapidly described this context, the paper will recall the main technical characteristics of these surveys, before developing the following discussion: can they claim to make up perfect tools for international comparisons of educational systems, and/or an efficient lever for some changes or policies concerning these systems?