Reading on another forum that apparently a Sheriff had offered to train 50 teachers for free to carry and conceal shoot handguns. He had 150 applications in 24 hours, so it shows that some teachers are for arming themselves.
As well intentioned as the above posts are, guns are in the DNA of the USA and probably always will be so. They won't give up their guns because their history includes being over controlled by a tyrannical government and they defend their right to make sure that doesn't happen again. It would be happening now if Hillary had won. She didn't win and they are still trying to pressure firearm bans far more than when incidents like this happened under Obama.
Until they can be convinced otherwise, there will be no change. Protest, march, throw tantrums etc. and you'll still get the same reaction from these people - the answer will be 'no, I'm not changing, I'm not surrendering my guns, and you can do nothing about it'. If the Democrats were to run with an anti-gun campaign at the next POTUS election they would still lose.
The USA needs to have an honest discussion with itself, involving all sides - the change (if it is to come about) has to come from within.