Dude we feel your pain over here at my house. We live on a well used route home for the High Schoolers and our blue box has been stolen twice, and broken many times.
I went to the school which said they could do nothing off school property, the cops claim they will come by more often but dont....so after a full winter of me watching between 2-3 pm last year (the time they walk by) and threatening an *** kicking to anyone who was doing anything, we haven't had problems since. They realized its hard to vandalize our house, or steal from us if they had broken fingers.
Seems people, kids, humans in general will steal anything that isn't nailed down.