This article focuses on the learning of the Lewis representation at the transition from high school to university, in France. Indeed, this notion is taught both in high school and in the first year of higher education but with different methods, which seems to hinder the learners. In this work, we observe 11th grade and higher education classes learning the Lewis representation to analyze the discrepancies in these two forms of learning which could be at the origin of performance differences. To complete these observations, we have developed assessments for learners to inform us about the effectiveness of different learning methods.