IMO, training and arming willing teachers is the way to go regardless of what our gun laws are today or tomorrow.
Agree with Brian that there are many school districts that cannot afford the constant services of local LE but paying for training and an extra monetary incentive to interested teachers may be a way towards getting things done.
Sadly, we have reached a day in our society that our innocent, unprotected children, while in school, that are noted 'no gun' zones, known even to the twisted minds, have become targets of easy prey.
Surely, history has shown us that there are no laws a 'lawless' person will adhere to when they don't want to.
Prohibition showed us we couldn't get rid of alcohol. People still drank!
The decades of 'the war on drugs" showed us we couldn't/can't get illegal drugs off the street no matter what laws have been instilled. Today,illegal drugs, especially illegal prescription drugs(opiates) are at epidemic proportions unseen in the past by any other drugs.
There are laws against drinking and driving...how many thousands get killed every year by a drunk driver.... How many bank robberies or home invasions???
This list could go on and on but one thing this list will prove is that for every law out there, there an element here in the U.S. that will break it.
Again, we can put a nationwide ban on all guns, but we know for sure that if someone wants a gun, they'll get it and use it for what they want.
Henry Kissinger once said in regards to the U.S. reducing our military:
"We need to be very careful as to the level in which we reduce our military forces because there is a certain point that shear 'brute force' will over-take strategy every time".
I think we've reached the point that we are going to have to have armed personnel in schools meeting force with force.