My son is a 3rd grader at a Catholic school.  Last year they requested parents to send in a "comfort kit" in the event of a lock-down type situation.  This was to be no larger than shoe-box size with a bottle of water, snacks, and maybe a note and/or picture from parents.  They also asked for a 3-day supply of meds for any child who takes them.  The kit and meds were kept in the child’s classroom (unlike his solu-cortef which is kept in the office).  This year they did not ask for these things (at least not yet), however, I took the box with water, etc. in and put the 3-day supply of meds in it.  The box was banded shut and was given to his teacher to be kept in the room.