Bullying among peers prevents children from enjoying their human rights in schools without the threat of aggression, harassment and discrimination. However, the States' duty to protect children from bullying remains loudly unexplored both in academia and in human rights practice. This article begins to fill a gap by articulating the States' duty to protect children from physical, psychological or relational aggression caused by other children in an educational setting beyond a punitive or individualistic perspective. This is the first study to operationalise the States' duty to protect children from bullying by examining the reliability of reporting mechanisms, the accuracy and disaggregation of data, and the quality of training for education professionals and future teachers in a country, in this case, Spain. The analysis relies on rigorous empirical research with focus groups and semi-structured interviews with 139 people in three Spanish regions, including parents, children, academics, bullying survivors and education professionals.