Let me start by saying that our last name is not common, so what I do works. We live in a very small school district also.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I just put last our last name on school items. If you have a common last name or a larger school dist, you could put first and last name.......I make sure to label (or initial) each part of a school supply too. I actually label the glue stick and put the initials on the lid.......name on actual marker, initials on cap.
Last name on the part of the backpack that would be against your child's back when it is on her. Last name inside lunchbox.
Honestly, I do not worry about getting school things back if they are lost (other than if it is dropped in the classroom...that is where the last name thing comes into play).....if a pencil or crayon type thing is lost, no one in this society will make the attempt to return it to the owner (not to mention that those items can be purchased very inexpensively). Yep, it does cost to buy it, but not worth the "security risk" that you are mentioning.
I would not worry about getting her a cell phone

we have to learn to let go and let them slowly leave the nest......it is hard, but necessary!!!!!!