Objectives: Starting from a reflection on the history of statistical reason (Desrosières, 2010), this contribution questions the relevance and the conditions of the usefulness of scientific evidence in educational policy-making. Through a critical perspective of the epistemological foundations of evidence-based logic, we propose analytical tools aimed at better understanding the resistance that educational reforms regularly encounter when they are implemented. Theory: Evidence-based policy in education is part of statistical reasoning and, more directly, an extension of evidence-based medicine (EBM). It aims to rationalise educational policies and practices through the use of research results, data considered as evidence, in decision-making. In this contribution, we propose to question the transposition of the epistemological principles of these two currents to the field of education. Insofar as the educational sciences are part of the humanities and social sciences, their scientific regime is different from that of the natural sciences. The SHS are historical sciences, which are characterised by the absence of “repetition of phenomena taking place in a constant or indifferent context” and which therefore rely on evidence that is “always dependent on a singular context of observation, measurement and argumentation” (Passeron, 2001). Due to their positivist epistemology, evidence-based approaches ignore this or do not take it into account. Methods and findings: To analyse the impact of the epistemological foundations of evidence-based policies on their implementation in the schools, we draw on previous research (Draelants, 2009) carried out on the reform of the abolition of grade retention in Belgium in the 1990s. The analysis of the design processes of the reform and of semi-structured interviews with teachers allows us to identify the knowledge and evidence that are left “out” - the willful ignorance (Weisberg, 2014) - and that contribute to the resistance that puts the reform to failure and, more broadly, to the distrust of public action and the expertise on which it is based. Significance: Evidence-based policies are gaining ground in many sectors of society, including education. The originality of our proposal lies in the perspective of the design processes of educational policies based on so-called "evidence" with the epistemological foundations of the evidence-based logic to better understand the resistance often observed in the practices of professionals. Our contribution aims to provide tools for analysing educational policies and to advocate for a broader definition of the evidence to be taken into consideration in public action in education (research and practice informed policy).

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