None really, wireless signals will not pass through a concrete wall well at all.
Tested a high-end Cisco wireless access point, worked through a doorway, soon as I moved several feet away from the door, no signal. It may get a signal though one wall, maybe. If you are wiring a school for wireless use that has solid thick walls, you'd pretty much need one access point every few rooms. Depending on the layout, windows, wall construction, doorways.