Education policy in England's schools is driven by the 'what works' agenda, characterised by interventions claiming to be scientifically objective and evidence-led. In this article I show how what works interventions reproduce anti-Black linguistic racism because to be perceived as someone who is 'working', racialised children must assimilate their language practices towards idealised whiteness. I present case studies of two teachers working in low-income, majority Black schools who rejected what works interventions concerning a commercially produced curriculum package and the so-called word gap, both of which framed racialised children as displaying linguistic deficiencies in need of correcting. I describe various institutional oppositions the teachers faced, including having their own language, expertise and evidence questioned by white management. I argue that the what works agenda is crafted by the state to delegitimise anti-racist efforts, and that for the state, what counts as 'working' is simply the reproduction of idealised linguistic whiteness.