Prior to instruction, a teacher/coach lets the football team scrimmage. during the scrimmage a student sustains a neck/spinal injury because of using an improper technique (head-down, helmet-to-helmet contact). the teacher/coach could be negligent because what duty was breached?

The coach has the duty of supervising the athletes if they are doing the techniques on training correctly. The incident may indicate that the injury can be caused by insufficient practical knowledge of executing the scrimmage. It means that the coach has accountability for this incident.