[Valpal1]

To rise above the random chance level real research and actual math is required.

But somebody intent on committing a mass murder might think doing it at one school while a planned drill is held at another would further ensure confusion and delay response, because everyone is preoccupied at the drill.

This may be an error because the 1st responders are all ready geared up so it may actually decrease response time.

[null and void]

The 911 operator who KNOWS there is a drill may quite reasonably dismiss a civilian call at a nearby address as just someone who saw the drill and in their excitement named the wrong school.

It might take several calls from different people for the realization that there really is an active shooter at the other school to soak in.

Say 3 calls, a minute each? That's about the average duration of an active shooter event. It's a long time if you're being shot at! It's also very fast for a response once the call get to the local LEOs