If I had a child in a public school, and was worried about a shooting in that particular school*, my instructions to the kid, starting at about 3rd grade, would be: "In the case of lockdown, through a chair through window, climb out window, using cover head for treeline and then home. You have about 5 min before the cops get there, so use it wisely. Once cops arrive, find cover where ever you are and hope they don't get trigger happy."
*expletive deleted*ck a lockdown. I'd deal with school admin later.
That said it's easy for me to talk, because I don't have that kid.**
*Barring a specific threat, the odds of a school shooting in any particular one of the thousands of schools in the US is astonishingly low. Picking a school and district with care can lower that even further, to the realm of statistically insignificant.
**It also allows me to be a little more dispassionate then some of my friends w/ offspring, so give and take.