Previous research did not highlight any positive effects of Geneva Educational Priority Policy on students’ skills (the Réseau d’enseignement prioritaire). Students in educational priority school underperformed compared to their counterparts in other schools, even when these schools had similar sociodemographic characteristics. In this article, we will explore a different method to measure the effects of this progressive educational priority device. More specifically, we will use a method based on time series analysis, and thus take account of different exposure time of students. This method consists in four different times for each school. This experimental design will give answers to the following questions: Is there a positive evolution of students’ results after the introduction of the device? And two years later?