Within neoliberal education systems, elements of marketisation are endemic and this brings with it the invasive pressures of performativity. Against this backdrop, discipline in schools is in many instances being more closely monitored and tightly controlled, with the implementation of strict and in some cases 'zero-tolerance' behaviour management policies. Can such an emphasis on compliance and control feed into greater educational inequality and marginalisation and if so through what means? This paper elucidates one possible mechanism through which the enforcement of strict behaviour management policies may fuel marginalisation -- namely through inappropriate use of internal exclusions, via an example of courtesy stigma that I term 'labelling by association with siblings.' This emerges as part of a wider ethnographic study into marginalised students in secondary school. The student participants have each spent time outside the mainstream classroom setting, working instead in an on-site withdrawal unit. Through poignant first-hand telling of his experiences, one marginalised student exemplifies and illustrates such labelling by association with his siblings and its consequences. He is adamant that this indelible association with his brother marked him out and stigmatised him, with very real and profound consequences for his educational trajectory or 'moral career', as well as for his permissible learner identities. Close monitoring of internal exclusions, or reforms promoting a more nuanced approach to behaviour management -- preferably in conjunction with a reversal of neoliberal inroads into education- are needed, to mitigate the barrier to educational equality which internal exclusion though labelling by association with siblings presents.