Look, I will be completely honest here. I was not a very good kid in HS in terms of law following. I think forgiveness and redemption is a lot better than tossing everyone out on the trash heap. But it is complicated.
I agree with this and I agree with your point about law enforcement, but the conversation wasn't about whether or not schools should expel kids for doing something away from school, but some of you were very absolute about schools doing nothing, the word nothing was used multiple times.
I can think of a billion things a kid can do outside of school that merits punishment at school. My senior year this meathead football player, wrestler, and thrower broke into the house of another girl on the track team and raped her. Do you think he had the right to go back to school after that and sit in classes with her while the wheels of justice turn? Doesn't her right to feel safe trump whatever we want to say about second chances, etc?
Same thing with the heil hitler salute example, outside of the scope of the law. Sure most kids at Manhattan High School have no reason to feel the least bit threatened by that salute, but what about the kids that do? Don't the Jewish kids and the kids of color have the right to feel safe at their classes? They're just supposed to walk past these kids like nothing happened, without repercussion? Another thing to, as far as the school goes. Let's say one of these kids caught doing that stomps out an Asian kid a week later. You gonna feel great about protecting the liberty of a 15 year old doing something they absolutely know is wrong, when the Asian kid is now has her jaw wired shut and she has 3 broken ribs? You just lost your job, got a kid maimed, ended up on the news, and got sued, for what? Protecting a high school kid who did something that they should have and likely did know what they did was very wrong.
Being a teenager shouldn't absolve you from consequences, that's a very dangerous precedence. Often the best or only vehicle for those consequences is through school or extra-curricular activities.