Weird how these teenage shooters are cold, mechanical, min-maxing, number-crunching killing machines... but they always pick their own school as the highest-ROI target.

It must be the tactical advantage of knowing the hallways.

Or... They're deep in a mental health crisis and actively want to die, and see the attack as a two-fer: kill the cause of my suffering, and then die to either myself or the police.

I'm sure a sign that serves as a daily reminder that "There's plenty of ammo here, your targets will stand their ground and not run, and you will definitely die instead of getting captured" will deter them at the earliest possible moment: Once they're already at the school, committed to dying, and packing heat.