They are influenced yes. Many kids with behaviors get a “cool down” time with a reward like play dough, snacks, candy, etc. the other kids catch on and start mimicking.

BUT that’s not my major concern as a teacher.

If a kid is screaming in the classroom and having a full on fit it can typically last 10-30+ mins. This often happens multiple times a day. That means the other students are missing out on potentially hours of learning. Every day.

If the kid is to the point of throwing objects, furniture, threats, etc (that would be ISS level as referenced in your OP) then that teacher now has to worry about the safety of 20+ other kids. We’re often left as the only defense and safety the other kids have. I’ve been a human shield many times. But, punched, hit, stabbed, you name it.

This is also traumatic for the other kids to see and shouldn’t be their “normal” at school. Teachers get no support or care after these incidents. I’ve gone to work with bite marks for weeks.