When we do testing in schools to determine giftedness it is the top 95th percentile of different tests. It wasn’t just reading and math but also nonverbal tasks (like tangram type things). We used state testing and IQ scores as well. We tried to create a whole profile of a child and then determine which ones met the criteria of requiring gifted services (95th percentile and above). I don’t think there’s a federal guideline so each state (or even each district) sets their own parameters. The twice exceptional kids were the ones with ADHD or other diagnoses. But yes, it was possible that these kids were not the “smart, model student” though I’ve had plenty of those as well.
We have threat assessments at our elementary school but we go through MANY channels before police are involved. Like, is the threat credible? Is anyone fearful? Does the child have the means? Is there motive? Someone making a comment that says “because they’ll blow up” would be a freaking conversation about school appropriate language not arrest and suspensions, for ANYBODY but especially kids with documented disabilities.