Methinks, if I were a parent and it was somehow impossible for me to homeschool or some such . . .
I'd inquire quietly about who the more alert, older, athletic male students were who came from wise families.
Then I'd meet with those families and with the 3-4 fathers and mothers and kids, arrive at a training program to strategies at least a handful of probable such situations. And I'd give the kids every skill and tool I lawfully could to handle such situations--especially insuring spiritual ones.
If possible, I'd see if older kids could be deputized and given more formal legal cover.
I'd want to experiment with things like pepper spray and perhaps injection options that might be legally carried in a backpack.
I'd strategize with some skilled stage magicians--not black magic but distraction sorts of trickery.
I'd experiment with ear piercing sounds and possible invention of hand sized modules capable of putting such sounds out.
I might experiment with darts and blow guns very concealable and insure that school and police authorities would sanction them for selected trained, responsible kids or just risk it with keeping them very concealed even from Xrays. Similar experiments and training with hefty rubber bands and perhaps paper clips or other rubber band shootable metal pieces hazardous to Jihadi's eyes.
Guess I'd just want to leave no stone unturned to provide my kids and the bus with as many options as possible and with tested ways to insure as many survivors as possible.
Forget the officials. They are either not going to be there in time or going to be awash in hand wringing politically tortured decisions for far too long.
The time to act is in the first 15 min or less.
imho.
What do I know. But these are the thoughts I've had off the top of my head and heart.
Slingshots
Wrist-Rockets with ball bearing ammo.