Education appears to bear responsibility on the one hand to do justice to society's need for reproduction and continuation, and on the other to do justice to the individual's capacity for and need to express resistance, critique and political action. How we navigate this problem is tied to how we understand justice. 'Plastic justice' is the suggestion that questions concerning justice and education might find a materialist expression instead of the usual transcendental ideals of justice. In this perspective, 'justice' appears not as an (un)achievable ideal but as a philosophical void that allows us to identify and react to injustice. An example of this is the void that allows for social selection -- in the form of admissions or exams -- that must be kept open if we wish to avoid encouraging social conformism and reproduction.