Education has moved higher up on the policy agenda and serving the public good has acquired new meanings. This entails demands to provide policy and market with instruments to enable evidence-based or at least evidence-informed choices in a so-called competitive global knowledge economy. This has, not surprisingly, led to a struggle about 'evidence' and the right to decide how 'what works' can be defined in education, which has consequences for school, professionals and educational research. The chapter explores this issue by means of Danish examples located within larger transnational agendas. Evidence discourse was initially a bottom-up professional strategy within the medical field. It was, however, reworked and launched into education in a more top-down move that has largely bypassed professionals. From this perspective, the author argues that the field of education and its professions may profit from adopting evidence as a floating signifier. This is, admittedly, a difficult endeavour as the evidence discourse is currently at odds with a majority of mainstream paradigms and understandings of school and teaching within the teaching profession and educational research. Taking the approach of the floating signifier could, nonetheless, be strategically useful in the struggle to expand the meanings of evidence to also reflect the experiences of professionals and the span of contemporary educational research. Three analytical distinctions are proposed in order to facilitate manoeuvring evidence as a floating signifier: evidence-based vs evidence-informed knowledge; global vs local evidence; and external vs internal evidence. [For the complete volume, "Evidence and Public Good in Educational Policy, Research and Practice. Educational Governance Research. Volume 6," see ED613293.]