You're claiming that civilian CCW would have prevented this. That's almost certainly not true, at least in the first classroom. Weapons would have been in backpacks, not in easy reach, and the shooter would have the advantage of surprise as well.
CCW may have prevented him from moving on to a second room -- but that presumes that the armed students had some idea of how to respond. Otherwise -- if they're just barricaded and waiting -- the guy still has the advantage of surprise.
Not to mention the likelihood of "friendly fire" fatalities, caused by armed students firing over the heads of their classmates.
As for "proper police tactics," well .... how are the police supposed to respond to something like this, where the shootings would have taken much less time than required for the cops to arrive?
What kind of quivering coward worries about “friendly fire” at a time like this?
So when confronted with an armed psycho, your preference is to wait for him to run out of ammo, as compared to taking the risk of being shot by a good guy on accident?
German jews who agreed with you went into ovens. If you choose the same fate, do us all a favor and don’t vote to disarm the rest of us.
Civilian CCW would not have stopped the first shooting? Perhaps, but it might have stopped it by the second or third. Weapons would *not* have been in backpacks (you obviously know little about CCW), but on the person of the owner, able to be produced in three seconds or so. Boot carry, small-of-back carry, in the case of the girls wearing skirts there’s always the classic “garter carry,” there’s Thunderwear.... lots of options.