Despite widespread commitment to inclusive education as government policy, global progress in the last two decades has been slow and uneven. This article explores the relationship between policy and its enactment to examine what conditions make inclusion available as a course of action within education systems. Focusing on learners with additional learning needs, evidence from the Welsh context is presented in relation to two policy turns in the last decade, the most recent of which is a turn towards a Fourth Way "professional capital approach" that appears to signal movement towards more inclusive education. It is noted that, at the level of practice and practitioner beliefs about learners with additional learning needs, these policy movements appear to have had remarkably little impact. Drawing on a hybrid model of analysis, we argue that the collective agency needed for inclusion requires an account of the belief systems of a range of policy actors, particularly in education systems where hierarchies of learners are fundamentally upheld. Using evidence from educational reform in Wales, we describe how conditions for collective agency for inclusion may be experienced as unavailable within education systems.