How could he do worse?
The Coward of Broward was perfectly safe cowering well away from the shooter.
A geography teacher in the building being shot at could scarcely show less resolve. Even if she froze (and a she-bear protecting cubs is unlikely to fold) the history teacher, the math teacher, the art teacher, and the ESL teachers are unlikely to ALL freeze!
The teacher couldn’t do worse even if he was only trying to protect himself.
I do think teachers develop a bond with their students though and would try to protect them.