How could assessment inclusively consider the diversity of students? In higher education, the most common answer is: through individual assessment accommodations. Inclusive assessment design has also been promoted to foster accessibility for all students. However, both of these approaches have largely drawn on the procedural understanding of 'inclusion' as 'enhanced academic outcomes'. In this conceptual study, a critical, socio-political approach to inclusive assessment is taken instead, considering assessment in its wider context of academic ableism. The rationale for Assessment for Inclusion (AfI) is formulated to harness assessment to promote the inclusion of marginalised students as fully accepted, agentic members of academic communities. Five practical principles for promoting AfI are introduced: rethinking accommodations, anti-ableist work, celebration of human diversity, student partnership, and interdependence. This study suggests that if mass higher education truly wishes to include students from increasingly diverse backgrounds, assessment needs to be rethought from the viewpoint of inclusion.