The article builds on prior arguments that research on issues of social justice in education has often lacked constructive engagement with education policy-making, and that this can be partly attributed to a lack of clarity about what a socially just education system might look like. Extending this analysis, this article argues that this lack of clarity is perpetuated by a series of contradictions and dilemmas underpinning "progressive" debate in education, which have not been adequately confronted. At the heart are dilemmas about what constitutes a socially just negotiation of the binarised hierarchy of knowledge that characterises education in the UK, Australia and elsewhere. Three exemplar cases presented from contemporary education curriculum policy in England and Australia are used to illustrate these dilemmas. We then extend this argument to a series of other philosophical dilemmas which haunt education and create tensions or contradictions for those concerned with social justice. It is maintained that we need to confront these dilemmas in efforts to extend conceptual clarity in what it is we are seeking to achieve, which in turn can better equip us to provide the empirical and conceptual information necessary to effectively engage policy-making to remediate inequalities in education.