Maybe it is a matter of what “being arrested” means. Perhaps being arrested is the same as being sent to the vice principal’s office for discipline.
I remember that in my senior year, a teacher who was assigned lunch duty, sent our whole lunch table to the vice principal’s office and gave us all school detentions for singing Happy Birthday at the lunch table.
The only reason that we could figure was that someone had drawn a picture of tinkerbell and stuck it to his door, and that he must have concluded that it was us. As far as I knew, it wasn’t. He was this little gay guy, but we didn’t do it.
They have police in schools because they have real criminals attending. Every child criminal that is on probation, must attend school as a condition of parole, you would not now that because their records are sealed.
Teachers do have to be told if they have a student in their room that has been arrested or convicted for a violent act.
Kids used to go to reform school if they couldn’t make it in regular school, they don't do that anymore, but that did not solve the problem, merely hid it back in the classroom.
I was in a teacher's classroom once and he told me look around you, there are the future presidents, governors, policemen, congressman, lawyers, bank robbers, ax murderers, serial killers, perverts....They all come through here.