Mc Kinney is about 8 miles north of where I live in Allen, Texas. One day while cruising around the town looking for interesting old buildings (and Fallout Shelter signs) I happened onto just that at Caldwell Elementary School, a fairly old school, probably late 1940s or 1950s vintage.
This is the school's auditorium on the east end of the building. This is an example of what I call "built-on-grade telltale Fallout Shelter construction." What I mean by that, is if an old building is built on a sloping grade like this it most likely was designated as a fallout shelter back when the national shelter survey was done. I went back up to the school one day ready to go through a big ordeal with the administration trying to explain what a Fallout Shelter is and how there is a sign on the building etc. When I got there I saw one of the school district groundskeepers parked right outside the basement door with the shelter sign over it. I explained to the groundskeeper what I was up to, and he was more than happy to help me out, and show me the basement.
Here is the basement door at the north east corner of the auditorium. The shelter sign is well-worn being exposed to the morning Texas sun for 40 plus years. There was no capacity marking on the sign. The foundation wall that this door passes through is about 12 inches thick.
This picture is looking in from just inside the doorway back into the basement. The basement was fairly clean and well lit although it was cluttered with old wood shop equipment.
The shelter is marked inside with a sign on the east wall. I found no supplies in the shelter after a thorough look in every corner.
This is looking toward the west side of the basement. There is a space behind the A/C equipment where I thought for sure I would find a forgotten stash of supplies. After crawling over the shop equipment to make it back there I found nothing.