Such an unannounced exercise could just as well have resulted in a heart attack or other medical emergency. It is not clear what the teachers learned much beyond what it is like to be shot.
Principal Cammie DeCastro noted that they learned that few people would survive among the 15 teachers. Only two were not hit by the spray of gunfire. It is not clear why actually shooting teachers was needed for that particular lesson or what they got from that realization even if they could not have anticipated it.