http://news.yahoo.com/claim-seeks-100-million-child-survivor-connecticut-school-003646074.html

A question I would want answered with gun control is "What do you want to achieve?" and follow that up with "How does eliminating guns achieve that?" ...

If someone has the intent to do harm and is ready to break the law to accomplish that banning guns won't prevent them from doing harm; because they will probably be able to get an illegal gun, and even if they can't they could find some other way (bomb, kinfe, car, etc.) to do the harm they want.

Actually looking here  the teachers were more often the victims than the ones who killed (just skimming it I didn't find a single teacher as the killer), and it was by those who didn't regularly bring guns. However; since you asked, 

"The late 1980s began to see a major increase in school shootings, including:"

And,

Thirty-five school shootings happened DURING the last assault weapon ban, including columbine. All after the "Gun-Free School Zones" act. 

Meanwhile in the 1950s, when my grandmother was a girl only twenty school shootings happend, and most of these cases were "revenge" cases against teachers. NONE of them were mass-shootings, and all of the murderers were late teenagers (15-18) who killed teachers or classmates on purpose with forethought, with the exception of two which were accidents. 

As for arming teachers, it should be a choice on the teacher's part. If they conceal-carry then nobody will know whether the teacher is carrying or not. And hence, a school would be far less of an easy target, because these mass-murderers want to kill as many people as possible and hence choose the most vulnerable targets. 

edit: " Prior to 1989, there were only a handful of incidents in which two or more non-perpetrators were killed by firearms at a school, including the 1966 University of Texas massacre, the 1974 Olean High School shooting, the 1976 California State University, Fullerton massacre, and the 1979 Cleveland Elementary School shooting (the 1927 Bath School disaster was a bombing, not a shooting, with a firearm used only to detonate explosives), the most recent shooting was the Sandy Hook Elementary School shooting on December 14, 2012. From 1989 to 2012, there have been at least 40 such incidents."

What passed right after 1989? Oh yeah! The "Gun-Free Zones act" 

we will be alright! Trust in Obama!

what is stopping them from doing that right now?

nothing.

if some teenager doesnt have self control enough to not shoot somebody when they get angry, first of all they shouldnt own a gun, 2nd of all nothing right now would keep him from already shooting people at school.

as for the teachers. if the are legally allowed to carry a weapon, then they should be able to lawfully have that weapon on them. and a gun wont do much good if its locked up in some locker on the other side of the building, now would it. teachers should either have the weapon on their person, or locked in a drawer in their desk.

 It’s redundant arguing what humans will do, humans have tendances to be evil they we never change but guns being so easy to obtain is a problem and makes those tendances easier to act on, much easier to stop some in a rampage with a knife then a gun. Now people might say guns people want guns they will get them use they will but people that do this mass shooting are normally your average joe and wouldn’t have connection to get these weapons illegally. It’s as easy in America to get an AK-47 as to get a knife licence in Australia, that doesn’t make you ask any questions? Banning all guns isn’t needed but banning semi automatic weapons is, what possible reason do you need a weapon designed for war. Quite frankly guns shouldn’t be allowed outside of the house, I’m quite sure you founder fathers would’ve approved of the right to bare arms if they knew these events would happen on a regular bases.

i would assume the school. since they remove ways for people at the school to protect themselves, the schools assumes responsibility for the saftey of the people inside the school. and the school obviously failed to provide adequat saftey measures.

Holy crap, one needs a license to own (or carry?) a knife in Australia? It does tell me something, but not what it told you. 

Yes you can't cary even a pocketknife into public and to purchase a knife you need a license which you still can't bring into a public area, yes this is over the top "nanny state" both between Australia and America there's middle ground .

In Israel they had a problem with soldiers commiting suicide via gunshot.  They changed military policy so that guns were not kept at home with the soldiers, but on base.  The rate of suicide via gunshot fell significantly.  The rate of suicide by strangulation rose slightly.  Overall suicide among soldiers fell significantly. 

Of course, the suicidal soldiers could have easily found other methods to off themselves, and some did.  But, the lack of easy access to guns brought down the suicide rate.  Putting an extra step between the thought and the action had a meaningful impact. 

Making it more difficult to get the gun adds several steps between thought and deed, adds more points at which suspicion can arise and the would be killer would be caught, and could conceivably alter the type of weapon that is used, possibly decreasing overall impact.