No.
What we are to
believe...is that an armed teacher could (a)lock the door to her classroom at the first sound of gunfire, (b) instruct her students to get beneath their desks, and (c) take a concealed position behind her own desk while covering the door with her weapon. If the bad guy kicks the door in or shoots the lock off, she takes him out. Her concealed postion gives her a tactical advantage which negates the lunatics firepower advantage. At the moment he kicks the door in, he doesnt know where she is but she knows
exactly where he is.
As far as the time needed to unlock and retrieve the weapon...the answer to that is
concealed carry in a secure holster. I post this video not for a gratuitous look at boobies, but to demonstrate how easy it actually is for women to safely and securely carry concealed regardless of what they wear. There are several women at my gun club who use this system. It works. A properly armed and trained teacher could make all the difference in the world the next time a lunatic shows up at a school.
FLASHBANG (BRA) HOLSTER: An Overview - YouTube