School plastic ID card printing systems
I know in high school, we all had to wear the plastic identification cards around our necks on lanyards or just somewhere visible so that teachers and others could see that yes we were supposed to be there. To this day I am still not sure how that would prevent a school shooting, as the child more than likely goes to that school and has an id card just like everyone else, but it does help identify those who did not have cards from those who did. My school even had a photo id card printing systems machine in the library in case you lost your card or just really wanted to pay for a new one.