Mother’s spanking of children was not necessarily “serious physical harm” sufficient for dependency jurisdiction absent consideration of other factors concerning reasonable discipline. Mother admitted using her hand or a sandal to occasionally spank her two children when lesser disciplinary measures proved ineffective. The juvenile court sustained a petition, finding that “hitting children with shoes is not a proper form of discipline, and it’s physical abuse.” Mother argued on appeal that the juvenile court’s finding against her was not supported by substantial evidence. The appellate court agreed, reversed the orders, and remanded for a new hearing. Section 300, subdivision (a) expressly provides that serious physical harm does not include reasonable and age-appropriate spanking where there is no evidence of serious physical injury. Whether a parent’s use of discipline on a particular occasion falls within or exceeds the scope of the statute turns on whether the parent’s conduct is genuinely disciplinary, whether the punishment was warranted by the circumstances, and whether the amount of punishment was reasonable. Because the juvenile court here did not consider the genuineness, necessity, or reasonableness of mother’s use of spanking as a disciplinary measure, its blanket rule was inconsistent with the law. Since the juvenile court applied the incorrect legal standard, remand was appropriate for the juvenile court to reconsider appropriate factors.