It sounds like I might be in the minority here, but even if it's easy to make fun of "a bucket of rocks", isn't the idea of instilling a philosophy of self-defense a good one?
If you're going to be in an environment where it is very likely the good guys won't be armed, it seems like rocks, books, pencils, and even loud yelling are better than "just sit there and hope you don't get shot." If you're in a secure room, that's one thing, but if you're in the same room as the shooter, a "what have I got to lose" philosophy seems like something good to instill. Even if the kids (hopefully) never see a shooter, teaching them to take their lives in their own hands seems like a philosophy that will help them later in life and maybe even counteract the SJW "safety above all" nonsense that is turning kids (and adults) into squishy, helpless marshmallows.