While I understand what you mean, I think the active shooter drills are pretty worthless anyway. They don't need to train them, because it is not a situation that unfolds in a specific way. Fire drills make some sense, but actual fires are pretty rare. Tornado drills make the most sense, because you have a specific short warning with specific reactions to protect as much as possible.
The teachers/ staff should know what to do, but terrorizing children with drills just doesn't really accomplish anything, IMO.