"Lockdown" is a term previously applied only within jails, prisons and other correctional facilities during riots or other serious security situations.
Now we have school "lockdowns" that the media makes a point of sensationalizing each and every time one occurs, for whatever reason.
I personally believe that this trend of lockdowns, "zero tolerance" policies, police and security guards in schools, etc. is conditioning to breed a culture of fear and obedience/soften the next generation up for further oppression.
After all, we've just about banned guns in this country and the crime rate keeps going up, so I guess the next step for the geniuses running the show is to make everyday life more like prison in a misguided attempt make us "feel safe."