This paper examines the importance of meta-analyses in scientific research to prevent school violence. These meta-analyses have contributed to produce critical knowledge (what does not work) and to identify interventions that are effective. However, whatever the acquired and advanced knowledge in the field, it is not as easily transferable and adaptable to public policies and this highlights a few limits of evidence-based policy and practices which is part of the illusion we have sometimes about the power of rationalism. This does not question this approach at all but gives it a more realistic and modest place.