"Kids saying shit is now equivalent to 'normal terrorist[ic] threat cases'?"

It's terroristic threats. That's the law most of the school shooting threats would get charged under. The real problem is that most states have automatic reporting laws, which means you have to report anything that sounds like a threat even if it isn't. This is the main difference between regular cases and school cases - you end up with a lot of junk being reported and potentially causing more harm than it was intended to prevent.

A 13 year old girl is not able to make a credible generalized terrorist threat against a large swath of the population, and besides, the first thing you should do when a kid starts making dumb statements like that is check in with them and their parents, not to call the police. Automatic reporting laws that lead to 13 year old girls being strip-searched are not something anybody should want.

There is an easy way to stop 99.9% of all school shootings, and it isn't 'automatic reporting laws'.

Children don't do "threads", that's why they are literally not of age. At most they say stupid shit that would be a threat if an adult had said that. The schools job is literally to teach children to not (want to) say that.