The promotion of performance measurement and international large-scale assessments (ILSAs) is often explained in terms of the rise and expansion of the neoliberal thought collective; in other words, testing constitutes a core component of neoliberal education reform. A less well-known feature of the neoliberal regime is its numerous precursors and antecedents in the 19th and 20th centuries. This article provides a study of such historical precursors in the treatment of children seen as 'mentally defective' in two emerging welfare states, namely Denmark in the interwar period and England in the immediate post-war era. Based on the records of municipal educational psychology offices in Denmark and the Birmingham Special Schools After-Care Subcommittee respectively, we argue that IQ testing and other metrics were integral to efforts at universalising treatments in the fledgling welfare states; but that the nature of such testing, numbers, and metrics components left them open to being gamed by various involved actors, meaning that the very instruments which were implemented to underpin the ideal of the universalistic welfare state to a certain extent worked to undermine it. In a similar fashion, the contemporary neoliberal education regime might face challenges from the metrics so intrinsic to its modus operandi.