I admit that my experience in armed confrontations is probably not as good as others here, so I'll defer to others on tactics and strategy. I just don't think that panicked parents with no body armor, no training, and no experience would be a good idea in a classroom packed with children and a shooter in body armor carrying a military style assault weapon. As for what the police and other armed men should have done, it's an easy call to say they should have charged in regardless of the danger to themselves. That is what we expect of first responders. I just think that the real problem was the lack of anyone there to make that call.
Perhaps an easier call would be for elected officials in the state of Texas to become more alarmed about the problem of too many assault weapons being available for public sale to any psychopath with a desire to take their frustrations out on innocent people.