Since the 1990’s, there is a paradigm shift in most educational systems: the initial input-oriented school monitoring shift to an output-oriented monitoring system. In this context, large scale external assessments of students achievements were developed both at the international level (see PIRLS or PISA), at the national level or even at the local level. In parallel, there was the progressive introduction of the competency-based approach in curricula and classrooms. Based on complex tasks, competency-based approach is however not without problems in terms of evaluation. Some authors even claim that large scale assessments and competency-based approach have conflicting logics and that both elements are irreconcilable. The aim of this paper is to qualify such statements by reporting an exploratory large-scale assessment combining a “classical” evaluation (with an important number of items to be corrected in a standardized way) and a competency-based evaluation with a diagnostic aim (complex tasks, decomposed complex tasks and associated elementary tasks).