The chapter focuses on the question whether a standardized learning potential procedure developed for Turkish and Moroccan children living in the Netherlands (the Learning potential test for Ethnic Minorities (LEM), Hamers, Hessels & Van Luit, 1991; Hessels, 1993) can be applied in a broader cultural context, while maintaining its psychometric qualities. Specifically, we set out to discover whether the LEM essentially measures the same psychological construct (construct validity), with a similarly high level of reliability, in French speaking Swiss children, as well as Portuguese and Spanish children living in French speaking cantons of Switzerland. Other validity criteria such as divergent and concurrent validity are compared to those obtained in previous research.