Man with gun vs. fourty men - Who should win?

The day after the Virginia Tech shootings, my English teacher brought up the event in casual conversation and mentioned school policy, stating "Remember that in the event of a gunman-type scenario, everybody needs to group up and huddle near that cabinet over there, away from sight." I brought up the point that the gunman could easily climb in through the window. "We'll lower the blinds so he can't see us," she said simply. I decided to also state that in this room there were thirty-five students, and one gunman. The students were outraged at my comparison. "Do you really expect us to overpower one man with a gun?" I was surprised that they didn't think twice at the thickness of their words.

Okay, Liberal Joe, let me make a comparison for you. Let's play pretend. Let's pretend that
the evil Dr. Turban has just entered the school premises. The alarm has just been raised. Now, this can play out either way. Allow me to demonstrate with the use of dramatic estimation, based on facts observed from other shootings, standoffs, and holdups, both in schools, banks, shopping centers, et cetera.

We'll use the "surrender" scenario first.

"FREEZE!" the gunman yells as he breaks down the locked door and points his 9mm firearm at the shaken students. "All students up against the wall!" Seeing no better alternative, the students comply, and stand at the wall, facing it. The teacher attempts to reach a phone to call 911. The phone is promptly shot out of his hands. "Try anything and you're a DEAD man," the crazed criminal growls. "You too, stand up against the wall." With all students defenseless, facing the wall, in fear of being shot, the gunman has the entire room secured. Everything is at his disposal. He didn't come in to steal money; if he wanted that, he would go to bank. He didn't want to hold anyone for ransom; the SWAT teams would be upon the building within minutes, and even if he made a reasonable trade-off, nothing would be stopping them from luring him out and capping him with a tranquilizer bullet. He came in for one reason, and that was to get revenge. Rage burning in his mind, he stood to the side of the students, raised his firearm, and opened fire. All 40 students in the room were murdered.
He managed to get a hold of 13 more casualties before the authorities finally arrived.

Gruesome, isn't it? 53 deaths... that could be labeled as the "most deadly mass shooting in U.S. history." Just shows you, anything is possible. Now let me show the alternative scenario.

"FREEZE!" the gunman yells as he breaks down the locked door and points his 9mm firearm at the shaken students. "All students up against the wall!" However, the students do not comply. They stay seated, facing forward calmly. "I said get up against the wall, or all of you are-"
The teacher, not wasting a moment, produces a .45 revolver from his desk and holds it level in the direction of the lunatic. The gunman panics at the sight of the weapon. One student at the back suddenly jumps up and attacks the gunman, pushing him over onto the floor. He calls for the other students to get a hold of him and pin him down. The weapon is immediately removed from the madman's hands.
Possible casualties? 4, tops. This is if the gunman decided to go ape and shoot as many people as he could before the students would be able to get him down. Seems miniscule compared to the previous scenario, doesn't it? It is.

Perhaps I'm wrong. Maybe everybody would have walked out alive from the school. But how willing are we to take this chance? If a man breaks into the room with a nine in his hand, though, I won't be the one who cowers near the cabinet. That's all.