All children in New Zealand have a legal right to an education. Yet, over the last five years over 20,000 decisions have been made annually to temporarily or permanently deny students of this right by removing them from school on disciplinary grounds. Surprisingly, little is known in Aotearoa New Zealand about the way in which the relevant law is interpreted and applied by those who make these decisions: principals. Responding to concerns over variation across schools in their rates of removals, this article presents findings from a socio-legal research study that explored secondary school principals' implementation of exclusionary discipline measures. The findings highlight significant variation in principals' interpretation and application of the statutory grounds for removing students from school. The implications of the study results are discussed with a particular focus on children's rights. Recommendations are made for law and policy reform, along with professional development.